I picked up this game months ago from the big Hollywood Video sale, and I've only just now played it. Pretty worth it... for 5 dollars. 7 is pushing it. And to answer the question of "is anyone playing online?" the answer is a big fat "not exactly." I did encounter one game after about 15 minutes of trying, but yeah, the guy just stayed in the lobby and didn't start the game. If you're in it for the achievements, you'll have to boost with someone, since 21 of them are Xbox Live only.
It plays like Battlefield 1942 with a Quake theme. If that tickles your fancy, give it a shot.