It's all relative but the Thurs-Sat of Tday is VERY busy. Some people don't mind it, they get there early and stay late and take breaks during the day since the hours are so long.
I, myself, would prefer the less busy time, less hours and would highly recommend the week after Tday. Even the week of Tday the Sunday to Wed is much better than the Wed-Sat, but it isn't as slow after the week after. That is the best. Figure out your schedule and then pick when to go. You can always make a vacation work : )
Just as a bit of background about myself: went in 2005 5 days before Tday and stayed until the Tuesday after (it was the busiest of the Tday trips, but I enjoyed it and the days before and after the holiday were wonderful!), 2004 was also somewhat busy, but for some reason 2003 was not for us. 2001 Tday was downright dead, no travel, everythign walk on! I was told that a lot fo people had to reschedule due to all the hurricanes, more people were there than usual for 2004 and 2005. The economy has also picked up so people are travelling more.
Jenn