The Christmas season in Celebration is really pretty and a lot of fun. It's not theme park quality but it's very well done. There's a big tree by the lake and "snowfalls" every hour in the evening, horse drawn carriage rides and things like that. I'm not sure I'd go out of my way just to see the decorations but if you want to get away from the parks and have a dinner in a different location, it can be a very pleasant break.
John