We just got back from our first summer visit to Disney in ---well, ever. I used to think people were crazy for going in the summer, but we were going on one of the cruises out of LA, so we thought we would just add on as a bonus.
Our dates we were there were August 12-17.
We were very surprised at the crowd level. We knew with gas prices and the economy that it limited the crowds somewhat, and read from the boards, and other people that it was not very crowded for typical summer, so I think we hit it lucky.
I remember walking down Main Street USA at about 1:30, 2 pm, and thinking, this is exactly what it looks like in September/October!
We enjoyed Fantasyland that was almost empty up to about an hour after park opening. Even going late (9am) on a Saturday, we only waited about 10 minutes for Astro Orbiter, and 10-15 minutes for Autopia at about 10 am...crazy. It was pretty much hit and miss though. Indy and other rides did get 45-60 minutes during peak times of the day, but we did really good hitting things early in the morning, and taking it easy the rest of the day. Even rides like Buzz, etc, never seemed to get much past 20 minutes (from whenever I passed them). Now the Neverland pool at DLH was a different story!
We were pleasantly surprised (weather was great!!!!), and would go back again if it was the same! We took some family members where it was their first time in the summer too, and they agreed that it wasn't bad at all...very doable.