OK, so now it’s getting hard. I’m onto World 7 now, and have spent far too long trying to do the second level. The previous world (Cobolt Caverns) was also pretty difficult, although I did manage to complete two levels first time. And the boss was really easy.
I’ve noticed that it isn’t really the same game as previous Monkey Ball titles, in that there’s less “balancing on a thin platform” to do. That isn’t a bad thing, it’s just an observation.