We were there Aug 20th through Sept 3rd and it wasn't as bad as early August. A friend from work went the first week of August.
We had 80-90 minute stand by waits for Soarin' (we used FP and did standy by once while Illuminations was going on and the wait was 25 mins., BUT since we were the last group on, we got to ride TWICE!! That was really cool.)
The best day was the day that Ernesto came through, we went to MGM and at 2pm there was a 5 minute wait for TOT and 10 minutes for RNRC. I took a picture of the wait times sign. It was lightly raining most of the day, but so what. We had ponchos. And there wasn't any lightning.
It was hot, but since we were there for so long we took lots of breaks and didn't feel like we were missing out. At OKW we had 2 days where we cooked out and swam all day.
If you can handle the heat and go the last part of the month, you shouldn't have terrible lines.