We were there August 8-13 and had a great trip. We were able to go on all the big rides twice by using Fast Pass effectively. Lines did get long but we never waited more than 20 minutes because we did early entry and used fast passes.
Sunday - arrived at 1:00 and went to Epcot. Got fast pass for test track (return time 7-9pm) and did Mission Space stand-by (20 minutes - our longest wait all week) and everything else in Futrure World.
Monday - went to early entry at Animal Kingdom and did EVERYTHING and were done by 3:30 (used fast passes for Dinosaur and Kali). Took a break and swam and went to MGM for Fantasmic (did stand-by on Star Tours - 15 minute wait around 7:00pm).
Tuesday - early entry MGM. We grabbed a fast pass for TOT and rode RNRC twice and went back to TOT. We did the movie ride, saw BATB and played Milionaire. Somewhere in there we had grabbed another fastpass for TOT and rode again before noon. Took a break and swam and headed to MK around 5pm. We got fast pass for Thunder Mountain (return time 6-ish). Did Haunted Mansion, Pirates, Philharmagic, Thunder Mountain, Tiki Birds, Treehouse, Jungle Cruise, Splash (15 minute wait just before Spectro), Thunder Mountain twice and saw Wishes. We could have done some of the stuff in Fantasyland - lines weren't bad -but my teen-age nieces had no interest (and I've been so many times I didn't care since this trip was for them and I'll be back in October and January!).
Wendnesday - Blizzard Beach and played mini-golf at Fantasia Gardens.
Thursday - early morning at MK for Buzz and Space Mountain (twice) and rode Splash Mountain again. We did notice that the lines in Fantasyland were long by 9:30. Finished up with World Showcase at Epcot.
It was hot but not as bad as I thought it would be. I live in Maine and it wasn't bad. We made sure we carried water bottles with us and took a swimming break in the afternoon.