Game's pretty good; a nice little time waster. Sound is fitting, story is interesting and gameplay is fairly fun.
The Rock enemies could be a bit easier (slower maybe), or you should be able to move while attacking. But mostly, like everyone else says, at LEAST put a checkpoint at the BOSS room. Tried for the Daredevil medal, could barely get past the room before the boss (the one with the 10 rocks sliding everywhere) and when I did, the boss killed me halfway. Pretty much gave up after an hour of trying.