We've been to Disney world a few times in November, and our last trip was November 16-23 2003. Personally, we prefer to go the week BEFORE Thanksgiving because there are virtually no crowds (ie., other than normal Disney crowds), and the wait time for most rides is between 10-30 at the VERY most. Normally early in the day and later in the evening there are no lines at all. My wife and I prefer less of a crowd, since we have 3 kids (8,5,3), and waiting in long lines or dealing with excessive crowds is too much for everyone. Last year, on our last day (Sat - Nov 23) we went back to MK before our flight and experienced lines of 1 - 1 1/2 hrs; as this was the beginning of the Thankgiving week for those that moreoften stay Sat-Sat. As for the weather, the weather is very comfortable in the mid to low 80's (still can swim)and at night it's a little cool, and would often wear a sweatshirt with shorts.
Hope this helps..and enjoy your vacation !
CK