I downloaded Bioshock from Steam for a measely $19.95 a while back.  If you're one of the six or seven people who haven't played it already, it's a very cool game.  Definitely a five... out of five.  It's not a very long-lasting game, though, as is typical of the gaming industry these days.  And it's not the hardest game in the world, either.  I played it on all three difficulty settings, and on the hardest setting, it started out kind of hard, but I got used to it after a while and it became rather easy to beat down the splicers.  On the easy setting, it was ridiculously easy.  Fun to whack everyone with the wrench, though.