I enjoyed the BioShockisms of it. I liked hacking stuff, taking pictures of stuff, and the sounds and the looks.
Also- becoming a big daddy in MP is pretty sweet. Finally a chance to get a good K/D ratio.
I'm not terribly into competitive MP, so maybe I'm not a good judge. But I quite enjoyed it up til level 20.
Anyways- I've played BL (what's the short version of Borderlands?) with my zombie friend, and then recently with My wife's brother-in-law's brother. I actually think (maybe ridiculously) that my wife will somehow fall for this game. So I think I'll get to start another character with her.
And maybe you and I can play sometime. You know, when you start a new character. On a date.