We were there from 2nd - 16th November, 2008 and weren't able to catch many of the Christmas highlights we'd anticipated being able to see during our early planning stages (due to the fact that the festivities started a lot later than they had in previous years). Similar (i.e. later) dates were in effect last year, too.
Based on previous years, we'd expected the likes of Osborne Lights and the Jingle Jungle Parade at AK to kick in at the same time as the first Mickey's Very Merry Christmas Party (which was 10th November in both 2008 and 2009), but they didn't actually start until 28th November in line with Holidays Around The World at Epcot which has traditionally begun a bit later than the other Christmas events.
All the Christmas trees and decorations at the parks and resorts started to go up before the end of our stay, including Santa Goofy's Holiday Village at Camp Minnie-Mickey.
Wishes changes to Holiday Wishes on the night of the first
MVMCP (and is shown on non-party nights, too). The first party date will also mark the switching on of the castle lights (so pretty).
You'll probably just catch some of the Halloween decorations during the first few days of your trip, but they won't be around for long. The last Mickey's Not So Scary Halloween Party was 1st November last year.
The parks were quiet during our trip, although we did follow our own strict advice of avoiding EMH days. The International Food and Wine Festival at Epcot is a not-to-be-missed event, but I'd recommend avoiding it at weekends and during the aforementioned EMH days. We also had fabulous weather, but, of course, that's not guaranteed.
