Troop Choices: Here comes a unit-by-unit review of the Troop choices, and how worthy each unit and upgrade is, plus how to best use each unit in your Tyranid army.
Termigant brood: Termigants by themselves have dropped by one point for no changes (other than Instinctive Behavior). Pretty good, right? Termigants are the typical Tyranid troop, what you think of first. These little bugs are pretty good at being pretty cheap, but that's mostly it. Scoring, cheap, and hey a Fleshborer. Do you need anything else? Well there are some options anyway.
Adrenal Glands: These work the same as on everyone else, but are pricey... they're more expensive than before and no one bought them then. It's worth considering because Tervigons no longer hand them out, but if you want gants to run or charge, there are Hormagaunts. (4/10)
Toxin Sacks: Again, pricier than before. In a less-CC focused environment these will just not be worth it most of the time. (4/10)
Spinefists: Strength 3, Twin linked. Garbage? Maybe not. Against T3, Spinefists are better than Fleshborers. Against T4 it's equal, against T5 Fleshborers are better, against T6 Spinefists are better and against T7 Fleshborers are better. In all of these, "better" is by ~0.3 wounds from a brood of ten. So, pretty close. If you know you're seeing a T3 army, go spinefists. Otherwise? It's so close that I wouldn't bother changing models. I prefer Fleshborers for the sole reason of being able to recycle them for Tervigons. For a free upgrade, you can't go wrong either way. This gets a (5/10) because it really is personal preference.
Spike Rifles: Hm, this may be the only rule left without a model for it... will it be gone in 4 years? Joking aside, it's a -1 strength fleshborer with +6" range. A decent trade-off, seeing as it is free. Of course it is statistically worse once in range, but range is longer. If you want to model it, go ahead, but you're worse than guard shooting now. I'd stick to Fleshborers or Spinefists. (3/10)
Strangleweb: This is now a strength 2 template with no special rules, or AP. Oh my. For the cost of a Flamer, you can get a flamer with two worse strength, but also two worse AP. Wait, what? Yeah, they did that. This is just one of the little things that makes me question the intelligence of Crudd- ahem, "the GW Design team". Leave this one at home... (2/10)
Devourers: The famed "Devilgant" has lost his Pod, so many people are turned off. However a Devilgant is 2 points less than before, which has to mean something right? That's still tricky on a T3 model to double their cost. Well, here's a subtle change that is actually great for the new book. Upgrades went from "all" to "any". Any gant may be buy a devourer, that's a full 30 or one out of ten. I wouldn't buy a full squad Devourers, but all extra guys after the first ten should consider it... put ten guys in front to tank and then have the rest Dakka away! This combines very well with the Hive Commander rule. (8/10)
Overall: These are a good unit to take, with their one weakness being Instinctive behavior. Otherwise they are cheap, often fearless and can pack a punch if you want them too. Plus, they can make a Tervigon Troops! (7/10)
Example: 30 gants 120
10 gants 40
30 gants, 20 Devourers 200
Crushing Claws: These up his combat ability, but really don't do that much for her. This isn't a line breaker beast, she's still best used by exploiting her toughness and spawn ability. (4/10)
Cluster Spines: Large blast strength 5, but loses 4 strength 5 Ap. 4 shots to buy it. Not worth it in my mind, as blasts at close range are bad for all the gants. I would avoid. (5/10)
Electroshock grubs: A strength 5 haywire template: For 10 points, not too bad at all. Sadly, Thorax swarms lost their rule to shoot in addition to the other two weapons. Still, this is a good way to remove hullpoints on tough vehicles. But she is not a close ranged beast, so not a must-take. However, she can outflank and surprise a vehicle. (7/10)
Desiccator Larvae: Fleshbane template: Good anti-infantry, but its usually not worth getting close to use it. (3/10)
Shreddershard Beetles: Rending, shred Strength 3 template. Good for taking out 2/3+ armor saves, but she should never be that close. (4/10)
Bioartifacts: Consider the Miasma cannon in this case, and this case only. She's a support beast, so range can suit her well, but don't expect to murder everything. Still it is not half bad. (6/10)
Overall: The Tervigon is much better as a troop. I think everyone is overlooking the facts and instead trying to compare the Tervigon to last edition. To be fair, I would have given it a 10/10 last edition, but right now it is still worth taking if you can appreciate that it's role has changed. Please don't charge it into enemy lines with no plan at all. In half of my games, the Tervigon just sat in the back and spawned while casting Iron Arm, and never got shot. It can do that still and still score. Play conservatively, (like in Venom cover...) and it is still just as tough to kill. Also, as a troop it can outflank with Hive Commander, where it can spawn and shoot. (7/10)
Example: Tervigon 195
Tervigon, Electroshock Grubs 205
Hormagaunt Brood: When you think Tyranids, you think a swarm of claws and teeth absorbing bullets until you just run out... the other basic troop for Nids, the Hormagaunt has a slot boost over last edition with his lower cost and +3 to run moves.
Adrenal Glands: Boy these are pricey! These got more expensive all over for giving fleet, but this is even for units that already have Fleet... inexplicable. Furious Charge usually won't be worth it. (4/10)
Toxin Sacks: Same price as before and does the same thing. Disappointing, but still not bad per se... Poison is nasty business! If you actually want these guys to go hunting instead of just tarpitting I'd consider this heavily. (6/10)
Overall: Not a bad unit, and as troops that can move fast, they're good for getting far off objectives... They're guaranteed a 10" move with open terrain. Average run though will be at least 13", which is quite good for last turn grabs if you want to hide them in early turns. Again, Synapse is critical at how fast they can kill themselves. Roughly 5/12 models will die if your units fails Instinctive behavior and can't roll a 4+. (6/10)
Examples: 30 Hormagaunts 150
10 Hormagaunts 50
Tyranid Warriors: Ok, this is one of the more controversial units in the book. They are the same base cost as before and have no Eternal Warrior available. But, many people point to a Meta dependent on Strength 7, not 8... Could these guys be useful? It's a troops unit that's Synapse. With the changes to Synapse, these guys could be useful as a line-holder guaranteed not to run. These guys come stock with Devourers and Scything Talons.
Flesh Hooks: At a bit less than 5 points, you get frag grenades and 2 strength 4 shots, at 6". This isn't bad but Devourers are better. Cheap is the new black with Nids, so pick carefully, but Flesh hooks are good for killing that powerfist first. (6/10)
Toxin Sacks: Standard poison, always good. These don't do THAT much but they aren't too costly. If you want to kill stuff up close these are ok, but that's not really their role. (5/10)
Adrenal Glands: Better than Toxin for the added fleet, but pricier. I'd say they're needed if you plan to run a CC squad, but will you ever do that? (6/10)
Spinefists: 3 TL shots strength 3, or Devourers? I'm inclined to go Devourers for superior range even if you miss out on ap 5 (Ha.) They aren't bad, but 12" is too short. (3/10)
Deathspitters: +1 strength, Ap 5. This will increase your killing power by a lot, which is always a good thing. Not too pricey, and justifiable on a sit-back unit. (7/10)
Scything Talons: Exchange 3 strength 4 shots for one extra attack? No thanks... (3/10)
Rending Claws: If one must go CC, this is how. Cheap, and can kill 2+ saves. This isn't too bad. (6/10)
Lashwhip and Bonesword: This is super pricey for Ap. 3, honestly it just raises the points on a fragile platform by too much. (4/10)
Boneswords: Like above, but slightly cheaper, and now slower. Just not good. (3/10)
Barbed Strangler: A cheap large blast? Why not? 36" is plenty for a babysitter squad, so really doesn't seem like a bad buy at all. Plus, pinning! (7/10)
Venom Cannon: I wish this was better, but at strength 6 small blast it can't quite kill vehicles or infantry... take the Strangler. (5/10)
Overall: Warriors aren't bad bare, but they get pricey FAST. There are too many things you "want" on them that cost points. Remember. Cheap is the new black. These are ideally a cheap Synapse unit that scores, not much more. (6/10)
Examples: 3 Warriors, Barbed Strangler 100
5 Warriors, Adrenal Glands, Rending Claws 200
Ripper Swarm: Ooh boy. Yeah these are iconic, but they were notorious for being atrocious last codex. I'm keeping an open mind, but there were no fixes here. Swarms, they get stealth, and aren't scoring.
Spinefists: Ok these aren't that bad I guess. A lot of shots, but not accurate and strength 3. Even twin-linked they'll miss a lot at BS 2. (4/10)
Toxin: Yeah, poison. Lots of attacks, but making a t3 multi-wound model pricier isn't good. (4/10)
Adrenal Glands: Fleet is pretty useful here, as at least they can make CC, seeing as they can do nothing else. No shooting, no scoring, they're a distraction. (5/10)
Deep Strike: Again, a distraction, but at least they can get closer before they die right? Actually one could conceivably DS and take a back-field unit by surprise, like 10 cultists. I've seen nurglings used like that. (6/10)
Overall: Troops that aren't scoring sums it up nicely... why would I ever use these? They're only 2 points cheaper than their wounds in gants, who can shoot and score. Yeah, that's a nope for me. (3/10)
Examples: 4 Rippers, Deep Strike 60
Genestealers: The cult favorite Stealers are remarkably similar to the past edition. Hint, they're the same. But, it's a new codex and open minds are needed. So, how do they fit in with the new book?
Scything Talons: for one extra attack these are very pricey, as there are no other benefits... Yikes. Loss of rerolls hurts here and these are too pricey on a pricey model to afford. (4/10)
Toxin Sacks: Poison helps here as re-rolls equals more rends. If you upgrade, this is how. (7/10)
Adrenal Glands: Priced more expensive even though they don't give Fleet here... just another inconsistency. Rends matter more than strength for Stealers, to really Furious Charge gives little here. (4/10)
Broodlord: Well this little boss is like a prime with claws in the unit. I wish he was Synapse, but oh well. He still knows the Horror, which is a VERY handy little Psychic power, which makes him a worthwhile upgrade. (8/10)
Acid Blood: Brood Lord only, same as always, way too pricey. (2/10)
Toxin Sacks: Again, re-rolling rends is nice. Costly but decent. (6/10)
Adrenal Glands: Again, already fleet and strength does little. (4/10)
Regeneration: Adding 50% to a units cost for that 4+ is too too much. (3/10)
Overall: Genestealers are still a costly CC unit with no durability, little speed and no assault grenades. The Horror helps here, so I say Broodlords are a must. But, they lack instinctive Behavior... a key factor. Consider infiltrating this scoring unit. (5/10)
Examples: 5 Genestealers 70
5 Genestealers, Broodlord 130
10 Genestealers, Toxin, Broodlord 220
Troops overall: Well there are only a few options, all are "decent" except Rippers. One Tervigon still seems a staple, and then try outflanking Devilgants or bringing them as a screen. Gants are better now while Tervigons have merits, and will be the base of most troops. Try adding either a Hormagaunt screen, a warrior brood for Synapse or a small Genestealer brood to disrupt things.