This is a great idea. I haven't had a chance to play it with someone else yet, but it looks like it could be a lot of fun.
The biggest weak point is the platforming controls. Sometimes the character doesn't jump when I feel they should. And, as others have said, it feels pretty slippery. Reaching the spikes at the top of the level was basically impossible.
I really liked the sound design. Perfect for this style of game.