Let's not mince words here. This game is great. If you're a fan of Warhammer 40,000 you'll appreciate the painstaking attention to detail that has been put into this game. Everything is as it should be, from the incredibly satisfying weapons to the absolutely massive environments. This is what 40k was made for: Over-the-top blockbuster action. A longtime fan myself, it's everything I imagined a 40k game could be.
Now that I've finished gushing my love for the atmosphere and feel of the game, let's get into the details of what works and what doesn't.
Gameplay- This is flawless. It's fun, simple, and intuitive. You can easily go from filling a mob of Orks with bolt shells to dropping a power axe into their leader's skull. The hordes of enemies are simple at first, but as the game progresses 'Wade in and kill'em' stops working and you need to plan your approach for each mob. One other thing on gameplay: Jump Pack and Gravity Hammer are the most fun I've had in a game in ages.
Voice acting- I came in expecting gravelly rage-fuelled marines, but got soft-spoken level-headed marines. As strange as it may sound, I much prefer this version. The marines never lose their cool, and treat hacking the enemies of the Imperium apart like it's a morning commute with bullets. This adds an air of dignity and gravity that lends itself fantastically to the 40k universe. These are the refined killing machines of 40k lore, not a crude convict or mercenary.
Atmosphere/setting/etc.- This IS 40k. There's simply no other way to put it, this is exactly the way a world of the Imperium should be portrayed. Everything is built on a colossal scale, and is rendered in breath taking detail.
Facial animations- I really hate to criticize this game, but it has to be said. The facial animations are wooden and unrealistic. It's quite distracting, to be honest.
Multiplayer- God damnit, why the hell is no one making splitscreen co-op anymore? I don't want to play with someone from another country, I want to play with my friends when they comes over. Sure, I can do that online, but it's just not the same. Other than that, it's not the best, but it's serviceable.
Fan Service- This game may not be as much fun if you're not a 40k fan. This is a game that doesn't hold your hand with the setting or bother to explain itself.