We had a great time in December. We stayed at POP, used fastpass wisely, and never waited more than 15 minutes for anyting, but averaged 5 - 10 minute waits even for ToT, HM, Splash, Space, and Big thunder mountains. Every once in a while the cheer leaders got a little loud, but it was fine. As PP said, decorations are amazing and weather was pretty nice. Go, and have a great time!