I've been in 2002 and in 2008. Both times we planned on spending a day in each park with a fifth day at one of the parks again. At the Magic Kingdom we intended to go on everything that Disneyland didn't have. That got us through about half the day so we had to cave in on seeing POTC, IASW, HM and Space Mountain. For the most part we weren't that impressed. It seemed like Disneyland had the better versions.
Over at Disney MGM and Animal Kingdom, we were surprised on how little there was to do at either place. At DHS, we did the TOT,RNRC twice, Muppets, skipped Star Tours, the tram was down, and the rest seem to be shows that we saw at Disneyland years ago. It was pretty half day. At Animal Kingdom, we did the safari, rafts and dinosaur and walked around looking at animals. I can't think of anything else that was worth doing there. Everest was ok but the Yeti didn't work.
However we loved Epcot and spend a few days hanging around there. My wife liked it because we got out of the heat for a few hours. Universe of Energy was her favorite because it was air conditioned. We had a final day we spent on the monorail, swimming at the hotel and walking around various resorts. That was pretty fun.
Everything seemed ok. It was just big and not as clean as Disneyland and extremely HOT! We are planning on going again but the way you guys talk about it, the place seems to have gotten worst. If we go, we are including a day or two at Universal with maybe three days at WDW. We could care less about fireworks and parades.