Like the other commenters said, it's brave to make a 3D game on your first try. You made it work though :)
My biggest issue is with the physics. The fact that the ball comes to a complete stop when you stop pressing a move button seems very unlike a ball. Also there's the issue with the moving platforms, but you already mentioned that's a bug.
I also agree that it starts a little too difficult. If you look at similar games (like Super Monkey Ball) the levels start as straight lines or simple curves with guard rails, then get harder until they're insanely hard at the end. This lets the user get a feel for the mechanics of the game before challenging them.