deany,
We go every year during the first week of October through Columbus day. We enjoy that time of year--the weather is usually warm and not too humid (except for last year), but we have found that the Friday before Columbus day the crowds really ramp up and the weekend gets really crowded. Last year we walked over to Epcot on Sunday, hoping to do a few things before we left on Monday, and we aborted the entire plan because of the crowds. The food and wine festival contributed to the crowds I'm sure.
I'm from New England and in my part of the country Columbus day is a holiday and the kids are off school and many businesses are also closed. From what I gather, it isn't a big holiday in the south.
It's still a pleasant time to go, just not as crowd-free as it is in say September. We are going again this year, so the crowds aren't enough to deter us.