Excellent!
I've played the full version. Though it's hard, and on the short side, that's a GOOD thing when it comes to the frequent, frequent checkpoints.
The game would take three times as long if there were a third as many checkpoints (this is how most games would have it). But instead, this game makes you beat every challange, but only makes you beat it once. If there weren't all those checkpoints scattered about, you'd spend all your time redoing things you've already beaten!