We were able to walk in to Cinderella's castle for lunch on New Years day!
I tried for months to get a cancellation but to no avail. I asked at the podium about 11:00, and was told to check back around 12:30 PM. Lo and behold, us and a few others got ushered in with about a 15 minute wait and had a great lunch.
SO, if you don't get a ressie, there apparently are a good number of people who don't show up for one reason or another. You might consider swinging by and trying your luck.