Made it up to the first room in the castle, but then I had a good hard look at myself and stopped playing.
Playing difficult levels for the sake of completing them seems rather hollow to me. Although I think the hardcore Knytt players (you know, those that keep insisting to the designer a level labelled hard is actually easy) should have a ball with this one.
For the most part decent and interesting combinations of challenges. Personally though I hold the view that if you're going to put the player through a hard time at least supplement it with consistent ambience/music and proper backdrops.