It plays great at the moment. I just feel the levels are a little too long. I think you make them shorter the player will get rewarded more often and enjoy it more. You'll also use level specific gimmicks less so they wont get tiresome.
There seems to be a bit of a bug when standing on active objects (i can only assume) He does his jumping/falling animation when standing on them.
Also I didn't like how the player can lose all of his/her life really quickly without a decent amount of invincibility time to get away from danger.