FWIW, if you're thinking post-xmas, try first 203 weeks in January (but before MLK day -- gets crowded for that!) We have gone during the week before / including xmas and it was great, but once xmas day arrived -- aye yi yi the HUMANITY was EVERYWHERE! On another trip (Jan 2-10), VERYYYY nice! Very low low crowds. I think some families pick Feb. timing because it isn't right as school goes back (like January) and is well before Spring break (and pre-break exams). And there's all the snow birds already down there. Not sure what impact NASCAR would have, but the Daytona Bud Shoot-Out was last wkend; then , as one person already noted, Daytona is this coming wkend. And President's Day is around this same timing. All that together spells crowds.
I wonder too if I've just become spoiled by the lower crowds of post 9/11 and now that the parks are picking up in attendance, I feel it more? Just a thought.
DH personally thought that the August crowds were no worse than xmas... he in fact preferred August because he was guaranteed weather hot enough to hit the water parks with the boys. (Dec and Jan can be iffy for swimming... we have been there when it's been in the 80's, and we have been there when it never crept above 50!)