This game holds interest for fans of 40k, but if you're looking for a great shooter, well, keep looking.
The first thing that strikes you is that the game wasn't meant to be a PC game. The options for controls, video settings, and online play are all contained in an external launcher, which is really quite indecent (I raised an eyebrow).
The first-impression does recover a bit - the menu graphics are slick and simplistic. Then you get into the opening cutscene. It's reasonably brilliant, except for the plastic-looking animations of the characters, and the nebulousness of the whole scenario. It is understood to 40k fans that vicious attacks and kidnappings need no explanation; they happen daily in the far future where there is only WAR. However, that doesn't excuse the game from having a coherent plot.
I opted to try the training my first time around - if only to get the complete experience. The movement of the main character, despite what some people have said, I found to be quite natural, and better-feeling than many games where the character seems to be as flexible and supple as a rock. The firing range was where it all fell apart. I was instructed to shoot a series of 'holographic' opponents who paraded back and forth on a small shooting range. It took me quite a while, because my Pulse rifle, supposedly a rather accurate weapon, sprayed shots like a garden sprinkler. This is a problem inherent to all the game's weapons - it's impossible to hit anything over ten metres away, short of a lucky shot. Of course, the sniper weapons are unfailingly precise, which makes them refreshing - but a bit incongruous.
Another fault is not so much to do with the training itself. The holographic Imperial Guardsmen would march back and forth across their ledges quite satisfactorily. However, the rest of the game's AI was only just a little bit more complicated than this. Enemies do little other than stand and shoot, or run up like they're going to hug you, then stand and shoot. Occasionally they kneel down for some variety. In addition, they seem to able to say nothing other than 'Be alert' or 'Be on your guard'. This seems to be more advice to the planer than any meaningful dialogue on the enemies' part, since they always say it when I am about to run into a group of enemies. I secretly utter a little 'thank you' as I reload my weapon, ready to mow them down around the next corner. The entire impression of the AI is that the developers decided that a 40k game with shooting in it would be cool enough for fans, so they didn't bother to have the AI do anything else. While they were at it, they thought 'let's be cunning and make the AI say things that *sound* intelligent. That way, people will think they *are* intelligent!' That kind of backfired - when a guard shouts 'Taking position!' while standing in front of you firing, it kind of highlights their stupidity, instead of providing the illusion of intelligence.
So the action isn't great. Maybe the setting provides some release? In a way, it does. The environments are designed capably, in a very formulaic way. As a fan of 40k, I thought it was quite cool to be able to see the inside of a Tau ship, or an Imperial prison - but that sort of wore off, since the environments were just plain dull. The Tau ship, while having this cool, organic exterior design, is just grey and squarish, with some shiny glowing bits and occasionally some interesting curves. The Imperial ship is oppressive and grandiose, and there is some seriously big architecture to see. But Fire Warrior seems so intent on constantly making you (try to) shoot enemies, as if it's the biggest thing since sliced bread, that you often don't have time to stop and marvel at the scenery, since you're always busy fending off attacks.
Now, environments aside - who can honestly say that 40k is an inappropriate setting for a shooter? It's about a universe perpetually locked in massive wars, and features some of the most over-the-top ideas in all of science fiction. Rapid-firing RPG launchers? Check. Lasers that blow your limbs off? Check. Chainswords? Check. CHAIN-AXES? Hell yes! But none of this over-the-top-ness really shines through in Fire Warrior. There is little noticeable blood, enemies don't really react when you shoot them, and they all die with characteristically over-the-top animations that make it seem like they're all self-interested, melodramatic actors in a B production of Les Miserables or something. Then, of course, the developers went all the way over the top and back down the other side sometimes - like when you hi an enemy dead-on with a grenade or bolter shell, and they literally explode into chunks of meat. The effect is just laughable, given the cleanliness of the rest of the combat, and the way the gibs bounce about like rabbits on steroids. You can see the developers knew that combat had to be bloody and visceral, but just completely missed out the point.
Of course, there are some moments when you are just impressed. Like when you blow an enemy away with the (underwhelming) shotgun, and they pirouette of their feet, slamming into the ground. Or you hit someone with a perfectly-thrown grenade, and their flaming corpse goes tumbling down the stairs. The high lasts for about a second, then you get dragged back into the monotony.
Speaking of monotony (and bad segues), Fire Warrior's developers had evidently not played any FPS games more recent than Doom. The mission objectives revolve around getting from point A to point B, killing every enemy in your path, and all too frequently with the aid of coloured keys. Yes, coloured keys. I was amused the first time, but after a few more levels, it became deeply unfunny. Warhammer 40,000 is not a coloured-keys universe, not to mention the fact that games have advanced slightly since those heady days of yore.
And I haven't even got onto the whole suspension-of-belief element. This is probably less of an issue for non-40k people, ironically. Because players of FPS games have come to expect God-like power within the realm of the game. The traditional FPS gameplay involves the player single-handedly tearing through hordes of lesser enemies. Fire Warrior follows that tradition closely. Given that the player character is actually one of the gruntiest units in the 40k universe, a Tau Fire Warrior (on his first day out, no less!), this makes as much sense as a fish with an umbrella. I laughed out loud when I took down a Valkyrie with my Pulse rifle - sure, it makes me feel big as the player, but it makes me mourn the fact that Kuju paid so little attention to the balance of the background. Don't even get me started on the mass-killing of Space Marines, apparently the most elite badasses in the entire universe.
These things could have been forgiven if the player was, for example, a Space Marine - or had a Battlesuit, or some other reason for being an uber-skilled pwning machine. In reality, the problem is not that the player is stronger or tougher than the enemies - it is just that the enemies are too incompetent to fight back. This is one of the saddest things.
Graphics: boring. I've said that there were some interesting levels, but when you get up-close, everything is kind of lacking in detail. When you consider that Halo came out two years before, the graphics seem even less appealing. Characters animate smoothly - but what they are animating is sometimes ridiculous. Ship pilots tap away at thin air, as if there were an invisible computer screen. Deaths, I have said, are dramatic and often amusing - which, in this game, is a bad thing.
Sound: mediocre. What sounds there are are decent, even if I personally hate the 'pew pew' Lasgun sounds. Enemy speech seems incredibly tinny, as if everyone is a Happy Meal toy. This could work for Marines or Guardsmen with helmets - it's a nice voice filter effect. But when it's same with bare-headed enemies...
The voice acting ranges from great (the much-touted talents of Tom Baker and Brian Blessed) to laughable (the Japanese-accented Tau).
I would conclude that if you're a fan of 40k and want to play a 40k game, you should find Fire Warrior somewhere cheap (that's hat I did). If you don't particularly have any infatuation with 40k, and you're looking for a good, fun shooter - then this game isn't what you're after.