Environment-centric fighting game. Major innovation over Power Stone is 4-player support, which makes the game feel very different from the 1v1 fights of the last game. Accordingly, there's much more of a “party” atmosphere, with levels that automatically shift through different phases and large environmental hazards adding extra chaos to the play.
This was always a rental for me, and good fun with friends. Before it came out I remember thinking the game really needed 4-player support and this would be definitively better; after playing a lot, I found myself sometimes missing the focused 1v1 action of the original, which wasn't really available in 2, so in that way the sequel didn't really replace the original. An interesting choice.
I would absolutely play the heck out of a third game if they ever made one.