I didn't participate much (and whatever hats I collected happened by accident) but I liked it, and it was very well designed and executed. One thing though - some of the hats encouraged "randomly click the vote button twenty times" type behaviour [that had caused huge frustration earlier this winter][1]. I'd rather if next year's winter bash dropped those hats that could be gained that way.

Other than that, I'm looking forward to seeing it again in twelve months' time.

  [1]: http://meta.stackoverflow.com/questions/155561/the-robo-approvers-are-killing-my-will-to-review-edits