My family (self, Dkids 8 and 4, and DGM, 67) went the last week in August in 2002 and we were completely spoiled. We went to MK twice right at opening time, and both days rode Splash Mountain and BTMRR several times in a row with no waiting until the lines filled up at about 11:00. Walkways were completely clear. We walked onto HM every day. Fantasyland was the only section that scared us, but then again, that's where all the youngest ones - and all their parents - go. We never waited more than ten minutes for an attraction or a meal until the Saturday of Labor Day weekend, but that day we made excellent use of Fastpasses and skipped rides with long waits. AK felt crowded and we waited a while for the Safari, but walked right onto KRR several times - in fact, we park-hopped a lot, going to AK just for a few quick turns on KRR to cool off. MGM was somewhat crowded, but we rode ToT three times in a row on two separate days, again, with no waits. Strangely, the only gridlocked attraction at MGM was Voyage of the Little Mermaid. Epcot was deserted the entire week. We stayed at ASMu and always had room on the buses and in the food court.
I went solo this past Easter and noticed a LOT more people at the parks and resorts. We're heading out again this Sunday, and I'm afraid the kids will be griping often about the crowds! School holidays prevent us from going during the least crowded times of year, but I was completely satisifed with our experience that last week of August and would happily go again during that week.