Found a rather important bug - I bought the Ladder ability and then reset the game progress thinking I was stuck - however, I appear to have still learned the Ladder ability in my new game.
Hmm... Wasn't in the mood, despite playing it all the way through, it seems. I'll abstain from voting though, as everyone else seems to be enjoying it, to be honest. :P
Think I have to agree with Froodjakle on the ninjas - the normal ones are all right, but the bosses can get to the gems in one cloak. My suggestion would be more weakness towards the meteor, or as mentioned by someone else a hotkey for the Meteor spell - at the moment it's a nightmarish test of reactions to kill the boss, often on the last stage.