This has all the makings of a great party game! As a single player game the longevity might be a little bit limited, depending on what you enjoy. The AI is good enough for sure, but this kind of things just works better with competitors where the winner can lord their victories over the losers.
Not much bad to say here: the art is cool, the sounds+music nice, the feel is there, and on top of all that it is works well, so any criticism becomes nits and matters of taste. If there was one thing I'd personally like to see changed it would be the course design... I'd personally prefer courses with a bit more speed and flow, and a bit less random object collisions. I generally also agree with those who would like a bit more instructions+introduction, with a progression of levels that introduce new stuff, and a good explanation of the initial rush to grab a chair, which I never quite got the hang of. Can anyone grab any chair? How does that make sense when you get to choose your chair before the race?
All in all, a really solid entry, one of those that just feels like a complete game already.