Actually, this is a busy time according to all the sites and books.
President's week is the 19th which is peak season. Nascar is the weekend before, and Mardi Gras is the 20th, which brings lots and lots of people from Louisiana! President's week doesn't always correspond with these other two functions, but this year it does.
I have seen some posts that say President's week is not near as bad as all the hipe! We always go early February, so haven't seen for myself!
Just remember: A crowded day at Disney is better than any day any where else!!