I like this game overall but its a mixed bag. This review is based on my first and only completed playthrough on Exterminatus.
TL;DR: I recommend it, but it outstays its welcome to the point of being 110% done with it when you finished the game your first time around.

+ The main selling point, the gunplay is G R E A T. The weapons are thundering and powerful, just like they should! The more powerful arsenal shake the screen just right to make you feel the impact of it, the humble Boltgun tears through standard infantry to give you a real perspective of the arsenal once you start fighting heavy hitters that shrug of that kind of calibre.
+ Dedicated Taunt button. Bring the zealotry to them in a delivery method more effective than the humble T-bag. Just wish it had actual gameplay effects like giving you a scaling amount of contempt or a short damage boost when done with proper timing.
+ Art direction is very nice. Chunky, but charming and enemies are well presented.
+ Bringing over the strength and toughness system from the miniature game is a great idea. It forces you to think what weapon to use where and it’s all very intuitive.

- It fails in the most important department of them all, leaving the customer wanting more. The game has a rock-solid start and It swings for the fences with its initial presentation but loses momentum around the halfway mark. I was ready for the game to be done at the start of chapter 3. I finished the game in three sittings, one chapter at a time. Would’ve been a solid 9/10 if it ended at chapter 2. If there’s DLC, i sadly won’t be coming back to play it.
- The game is easy. On Exterminatus (which feels like tuned up “Hurt me plenty” instead of “Nightmare”), it was rarely a challenge. The game drowns you in resources and the game only truly felt alive and difficulty appropriate during the final boss encounter which was a true high-note! Don't be afraid to use your entire arsenal. There's always ammo around the corner.
-The environments are lacking and are exactly what you’d expect from 40k. Sandy dunes, gothic cathedrals, factory. You’ve seen it all before. It’s boring and blends together quickly after chapter 1. Maps aren’t built intuitively; it tries to adhere to the labyrinthine structure of 40k too much resulting in you running in circles over and over.
- Speaking of maps, the lack of a map hurts the game. Everyone I’ve talked to that owns the game all says the same thing. Why is there no map? Even Doom had it back in 1993 had it, so why can't this game?
- Enemy AI variety is a little lacking. Either they charge you or they shoot at you. No enemy really controls an area like say, an Archvile, you don't really play around most enemies. Shoot and scoot. Little thought going in to it.
- Some enemies are too spongy on Exterminatus and I’m specifically talking about the Toads of both varieties. If I could provide feedback, I’d have the first half of their HP be shielded to represent their increased toughness thanks to Nurgle's blessing and when that shield is broken, have their strength check lowered.