I finished the game last night and liked it a whole lot...
The story only got more interesting the further you progressed and they've upped the stakes on the moral decisions too. (Although after playing Mass Effect 2 it stills seems a little too black-and-white.
) It really gives another perspective on Rapture and fleshes out its world and characters some more. I was very impressed with the combat this time around as well. You could actually prepare for fights a little more elaborately. The Big Daddy/Little Sister aspect of the game was pretty incredible, with a very memorable section in particular.