It's an incredible game, but I have one gripe...
My only real gripe was the introduction of Sephiroth way too early. The original game references him a lot, but didn't officially introduce him until Kalm. It adds mystery to the story.
Introducing him so early and multiple times just seemed like fan service shoved in my face. I know the game as a whole is fan service, but they should have held back just a bit.
Otherwise, it's incredible so far.