Definitely a bit difficult for me, although I don't play platformers too much and I know that there is an audience for difficult ones. I want to say that some of the controls were weird (jump seemed to activate a little bit after I hit the spacebar; I seemed to slide a little bit when coming to a stop, etc.), but it's possible that's just me making excuses for how bad I was at it.
The art is awesome. Love the backgrounds and the player sprite. Just wish I could have gotten a bit further. In fact, I may come back to this!