It's a VERY different game, and very refreshing (if depressing at times).
It's got ALOT of replay value, as you need to play it several times to see the effects of your decision. Every once in a while, a game turns up that redefines a genre, and this is one of them. It certainly deserves more than a 85% IMHO. More like a 95%.
There were a couple of bugs in the initial release, so make sure you go online and get the patch that sorts these out.