Awesome game! Minor gripes I have so far is that if you die you restart the level with the amount of health you started it with. However, hasn't prevented me from progressing so far. And in the "Bigger and Boulder" level I had a stutter which made me drop in the pit with lava because I missed the elevator.
I hope the game autosaves, because I want to stop :-)
Edit: It does autosave, nice!