I've never heard that it's been packed. People are still recovering from Christmas, and it's cold outside.
The kids have the day off school, and most companies are closed, but I'd imagine it would be like a normal Saturday.
We just got home from going to IOA and US on mon (MLK) and tues. There really wasn't a crowd. We were FOTL and only used it a few times when the wait was 20 minutes. The highest wait time that I actually saw was for The Mummy (25 min.) and Hulk (25 min.). I would say it was not a huge crowd day.
We were there for the MLK holiday in Jan 2005 and I have to say it was pretty packed! We had purchased the fotl pass and were so thankful that we did. There was at least a 20 min wait on most rides. I actually felt a little guilty walking in front of every one-yeah right...
Yeah, the parks weren't as busy on MLK day as during the Christmas season. I took the day off and went with some friends, we were able to get on mostly everything we wanted with less than like, a 20 minute wait.