I've played about 3-4 hours of the game and was quite disappointed. Because of the 64' controller, actions were clunky and quite hard to move sometimes without falling off. I'll probably go back to finish it someday though. I think I'd prefer something like Super Mario Sunshine.
Though I have to say the fact that you can make a level is pretty neat. (Anyone even use neat anymore :V?) I know you can do it with other games but for a N64 game that's nice. Nothing like Excitebike though xD