OK I just beat it last night. Stayed up past my bedtime and powered through the final section. As I've said in another thread, it is easily one of the best new games I've played in recent years, and by far and away the best Western developed RPG (sorry Witcher 2, my computer sucks and I can't play you). I have only two pieces of criticism:
1. The bosses. Yeah, this has been repeated ad nauseum, but it really did bother me. For ever one of them I probably spent 20 or so minutes dying instantaneously before getting a handle on it. Considering the time it took to reload my save state, this was a major pain. And I was playing on Give Me a Story difficulty, if it matters at all. There's a lot more to complain about with them, but it's already been said.
2. Dungeons way too long. Don't get me wrong, they were designed very well with lots of neat things to find and ways to do things. I am was impressed at how naturally I was led in the right direction, even when it seemed like I wasn't sure if I was taking the best route or not. But towards the end of the game they started draining on me. Playing stealth games is taxing mentally. Making dungeons that long didn't provide me with the relief needed to calm down and relax. They needed more sections like Detroit and Hengsha to break things up.
Anyway, I'd probably give the game an A or A-. It'll just depend on how much those two issues really bother me two or three months from now.