Just sank about five hours into this game. I'm having a lot of fun. The hub city is a lot bigger and more interesting, and theres a lot more stuff to do in it. The early game slog that was present in the first game is gone for the most part, since you aren't limited to one instructor at a time anymore, and can therefore pick up new techniques and extra levels very quickly. As a result, the difficulty curve in the story missions are a hell of a lot smoother than it used to be.
I haven't played enough to give any kind of full review, but I can safely say that its made a strong first impression.