Yes, about 9-10 years ago we went the week before Labor Day and had a wonderful time. I think a lot of schools around the country start back in August--in Washington State, we don't start until the Wednesday after Labor Day.
We stayed at the Paradise Pier (before CA was completed but it was being built) and on our first afternoon in the park we rode the monorail in, walked right on to Space Mountain and had the best time ever. I don't recall waiting for any of the rides. It's possible we waited for a few but if so, they weren't long at all.
The next visit was probably 6-7 years ago and we went at Spring Break

. It was not nearly as magical but still fun. We are going next week and expect killer crowds but I read another post stating it might rain. Being from Washington State, we don't let rain stop us from much of anything so I'm hoping it does rain and the crowds will thin out a little.
We also went to WDW a few years ago when they had all the hurricanes. One caused us to stay in WDW a few extra days (sad, huh?) and definitely cleared out the parks. My kids missed the first day of school because of the hurricane so they had a fun story to tell their classmates--there are no hurricanes in Washington--just wind storms and small earthquakes (and volcanic eruptions every now and then). The hurricane didn't cause much damage (I think it was a level 2-3 so it was small) but that's most likely because of earlier hurricanes that did cause some damage--there wasn't much left to break or topple.
At the times we went when there were low crowds (end of August) it was still fun and there were longer park hours and plenty of shows to see.