Well Nerds has a
review of the game written by some wise being who is worthy of everybody's praise, I imagine. Essentially it's a hugely atmospheric game well worth playing. The city of Rapture has a lot of character that really draws you in, the game's few characters are well-realised and all have their own interesting story, and if you take advantage of the plasmids and hacking instead of opting for playing it as a shooter you can get a lot of variety from it.
My only real complaint is the lack of replay value, which I imagine is why it isn't talked about as constantly as other games these days. In theory it's possible to expand the game's length by setting your own conditions or roleplaying (don't use guns, don't use plasmids etc.) but you can see pretty much everything in the one play through. As I literally just posted elsewhere though the 360 version just had a minor update setting a new challenge, and if it heralds the start of additional content then that will take care of that one minor issue.
Either way there's a chunky downloadable demo for PC (I got it through Steam) that has you play through the start of the game and should give you a feel for it and how well it runs.