We went to the first MNSSHP this year, which was in early Sept. Worked out really great for us. I think we waited 20 minutes to get our photo op with Capt. Jack Sparrow.

No one knew he was going to be there until he showed! DH and I were going to ride POTC just about the time the party started, meandered by and there he was! Without much line! W00T!
The good: not that crowded at all. Everything is fresh and new and fun. Also, it's cheaper.
The bad: if you are in costume and the costume has any weight at all, it will be hot! DH is going as the wizard Harry Dresden next time we visit (2013) leather duster and all. He expects to melt directly into the sidewalk before we are done. We may even go a week or so later just on the feeble hope that a cool front might move through and knock the heat down a few degrees!