We went on opening night in 2002, which was the Sunday evening after Thanksgiving. I had read how wonderful the party was & how uncrowded it was. Not that night! MK was far more packed that night than it was at any other time during our stay. We watched the castle-front show and then saw the parade. The parade was fantastic! Then, we had a great spot to see the fireworks, so we waited another 30 minutes for the fireworks. Only the fireworks never came. There was some technical difficulty, so we never saw the fireworks. Heard later that they finally had the show after 11:30. Our kids were small, so we didn't stay until the end. And it was unseasonably cold that night -- in the low 30s! We left feeling like we had wasted $100.
Last October, we were at WDW during the MNSSHP, but didn't go. We knew others that were there the same week as us who went and loved it. They said it was way better than the Christmas party. We're going back next Oct & may try it then. Just on a week night & not on opening night!
Even though we didn't love MVMCP, you might. You might go on a night when the crowds are lower, the temps warmer, and the fireworks actually work. Which ever you choose, have fun!
Christy