When to go to Disney World?

I'm in Disney with my family right now (early December) and I have found it a really great time to be here. The lines aren't too long, but it definitely isn't dead.

According to "The Unofficial Guide to Walt Disney World 2009," early December is the best time to go.

This guide book quotes one man from Ottawa who went in Early December saying

"It was the most enjoyable trip to Walt Disney World I have ever had, and I
can't imagine going back to Disney World when it is crowded. Even without the
crowds, we were still very tired by afternoon. We will never go again at any
other time."

My one piece of advice would be to bring some long pants and a jacket. It's still Winter, even though you're in Florida. The weather can be in the 60s and dip into the 50s and 40s at night.