I've definitely got my money's worth from this one, there are a lot of interesting emergent qualities in the game and the map has a lot of secrets scattered around it for you to discover. This game took up my evening for a few weeks when I first got it, so well worth the money in my book. I still come back to it from time to time as it's under pretty active development.
I really enjoyed testing the limits of the engine and using the wand system to craft interesting physics things.