We love the extra parties and would do one in a second given the chance. We did the Christmas party a couple of years ago and loved it. We went on the last night a few days before Christmas and the park was kind of crowded but I didn’t feel like it was packed. We weren’t there for the rides, we can do those any time, we were there for the atmosphere and the special activities. It really was magical.
The last Pirate and Princess Party we went to wasn’t crowded at all, all the rides were a walk on and we did all the extra things with no wait. I would plan my trip around another P&P Party if Disney ever brings it back.