Remember the days of Duke Nukem and Quake? Like that - only more gore, and a boatload more cursing.
In short: Epic.
It lacks vs. Multiplayer - but it wouldn't really work anyway, so it's not a huge loss. Anarchy mode is pretty fun, when you get a good group of players who know what they're doing: Like many modes of this kind: It's all about teamwork. ( Think Hoard in Gears - Wave after Wave of enemies to just blast. )
The story is a little weak - but you don't play these games for story.
Echoes is fun too - and there's something strangely compelling about just trying to set a higher score than a friend of yours, or some random person on the leaderboard.
Overall, I'd say it's worth getting if you don't mind the lack of VS.
If you haven't, I'd recommend trying out the demo on Xbox Live, PSN or PC - depending on what you own. It's a single stage demo, of the Echoes mode - set in one of the later maps.
erm, bought Battlefield Bad Company 2 on the PC, my flat mate bought Bulletstorm for the XBox so ive not bought it myself yet, but will probably get my own copy soon enough. erm, nothing exactly recently, got the new WoW expansion Cataclysm although thinking about it, ive played WoW for about 4 hours in like the last week