We just returned from NYC last week and have decided to return in December to see the Christmas decorations. My original plan was to come this past December but I just couldn't get it planned out. In retrospect I am glad our first trip was at an "off-time" as opposed to the craziness of the holidays.
We want to stay on the UWS this time, I think it will be fun to be in more of a residential area at that time of the year.
One thing is for sure, no Times Square and no Chinatown. Been there, done that, don't care if I never do them again! ;)