We went last February (and going again Feb 24 - Mar 1), and EMH is both good and bad. Crowds walking around the parks are much smaller, but attractions can have long wait times.
Bad:
Animal Kingdom - not sure what EE will do to this EMH, but when we were there last Feb, it got dark by 5:30/6:00, so the only attractions open were a bug's life and Dino. Bug's life was a walk in (about 5-10 minute wait), but Dino ran out of FP's, and was a 45-60 minute wait. Dino land was really the only open area. Later in the summer, the safari and other attractions MIGHT be open until dusk/dark, so that would help spread the crowds.
Epcot:
bad becuase FP's for both TT and Mission Space were way into the night (11:30 at 9:00pm), and wait lines were very long. Now that Soarin has been added, that might help spread things out. Other attractions are literally walk-in such as Shrunk the Audience and Figment.
MGM
Better, but again, the 2 big ones - Rockin Roller Coaster and TOT are packed, but many of the other attractions are walk in, to very short wait times.
MK -
Probably the best of the bunch, at least when we were there. We did 2 things - 1, while the parade was on, we concentrated on Buzz and Space mountian. Once EMH hit, we concentrated on the other major attractions, and it worked out well.
If you don't get additional answers (I'm sure you will), I will udpate once we get back in about 10 days.