As a lurker around these parts i'd like to post my opinion of the voices if I may.
Master Xehanort/Nimoy: Great overall. From when I first saw the trailer I was the complete opposite, from seeing the streams, and what the leading trailers presented I really enjoyed his performances as a "badass antagonist".
Eraqus/Hamill: A different presentation compared to the original, but either way Hamill was amazing as he normally is in the end of it all.
Aqua/Holland: Lackluster was my original interpretation of her performance. She did get better, but nothing close to subpar, or "great"
Ven/McCartney: This was amazing, not just an exaggeration, but literally amazing performance from McCartney. In my ears I noticed a bit of differentiation between Ven's, and Roxas voices kindly.
Terra/Dohring: I was one of the cou that originally wanted Troy Baker for the role. Dohring unlike Holland improved heavily of the course of the game, I don't know if the people who say he has little emotion are listening to the same guy, but his performance was excellent, and kindly surprising.
Vanitas/Osment: Truly the star out of the cast. I know Nimoy, and Hamill are others high gems, but HJO proved that the original range fears, and his voice capacity can range, and achieve Van's coin personality.
Lurkers opinion = Finished.
