We attended the Oct 4 party and had a great time. We drove up from Carlsbad (we were really on a Legoland vacation with MHP thrown in) and got there at 4. It was a little crowded with the overlap between party guests and regular attendees but that was to be expected. As soon as we got there we headed to Blue Bayou for dinner and were able to get seated in less than 5 minutes without reservations. That gave us a chance to relax with a nice dinner and ride Pirates before the real party started. A couple of observations:
1) If you are interested in rides (that was our primary goal since it was our only time in the park) the advice about hitting rides first and trick-or-treating later was 100% dead on. For example, prior to being roped off for the fireworks that didn't happen, every ride in FL was a walk-up except Pan which was only a 10 minute wait (I haven't seen it that short before). In previous years we focused on the other stuff instead of ride so a ride-centric party was new for us so this helped out a lot.
2) Also, having a little girl made meeting princesses a priority. Luckily since we were able to get to the Fantasy Faire right at the start of the party there was no wait. The lines seemed much longer later on.
3) The only waits we had were for HMH and Pirates at the beginning. Space Mountain looked busy as well but we didn't try to ride it since my kids are not coaster fans.
4) I hate that the fireworks didn't go off and it made things briefly chaotic but not too bad.
5) Other than the trail by Rivers of America the trick or treat lines moved quickly. Even with focusing on rides, we still had huge amounts of candy.
6) Our only complaint was we had planned on getting our daughter a new princess dress and decided to wait until after the party to get her one on Main Street. We were told by several CMs that the stores would remain open as usual but it turns out that some of the stores on Main close at midnight for special events (including the one with princess costumes, I can't recall which one it was). However, on the bright side, when we talked to the folks at City Hall about this, they were able to contact World of Disney in DTD and let them know we were coming and offered us assistance in picking the costume. So even in what could have been a downer close to the evening, the folks at
Disneyland went out of their way to help us and we really appreciate what they did.
I also have to say that after going to both MHP and Legoland's Brick or Treat party there is absolutely no comparison. I won't go to much into Legoland's party but I will say that I am SOOO happy we decided to include the Disney diversion, the trip would have really been missing something without it.