It seems to be pretty much the same thing except bigger.
I really liked the first one, but by the end of the game the Nemesis system and the core gameplay loop had kind of worn themselves out. There's some new stuff added to the sequel but nothing that seems so amazing that I need to play it. I'm actually kind of turned off by the fact that the reviews say you'll need 40-50 hours to do everything, which is a large investment in doing the same routine over and over.