Can you say nightmare on Main Street?? Plan on all of the parks being packed to the hilts with people and very long lines for attractions. I would strongly recommend making PS as soon as you can. The MK, MGM & EPCOT are usually open until 1am on NYE and during the week between Christmas and New Year's till about 11pm. I went over New Year's once and although it was fun to do something different for NYE, I would never go during that time again. It was just too crowded for me.