I bought Space Marine before it came out *hipster*
(Translation: I pre-ordered)
Space Marines were my first 40k army, and are still my main one, and since the game looked awesome, I made the decision that I was definitely going to get it.
First things first: if you don't like slaughtering hordes of orks, alone, with a chainsword, then this game isn't for you. If, however, you do enjoy beating the giblets out of fungus-apes who are too stupid to run, then great!
I''m not going to lie: this game is pretty. I had to lower all the settings so that it would actually be playable on my laptop. It still looked like this:
You play as the guy in the middle. Not the bald dude on the left, or the old dude on the right. The middle one. He's the captain. Captain Titus.
He's also tall. Really tall. And covered in ork blood. Don't worry, that gets disintegrated by the shielding after a while, so that you can bloody your armour again. And again.
The story isn't too bad. There's an Ork Waaagh! (invasion force for those that don't speak 40k) attacking Forge World Graia. Forge Worlds are important strategic assets, considering they're covered in immense factories that build all the weapons, ammunition and vehicles that mankind needs to just hold off alien threats across the galaxy.
There are also big cranes carrying big guns for bigger war machines. The Orks want these weapons of mass destruction so that they can massively destructify all who stand in their path. This is one of them: a Warlord-class Battle Titan. It's bigger than Titus.
Multiplayer is reasonably balanced, unless the teams get stacked. In which case, one side gets raped, but that's pretty much what happens in any multiplayer game with stacked teams. Speaking of teams, both of them are Space Marines. One side is the good, normal Space Marines, and the other is the spiky, Chaos Space Marines.
The customizer is pretty cool too. Check out a video by THQ about it
here.
I've probably said enough now.