Most of my Disney trips have been the first week of May or during October. Actually, the first week of May is my favorite time to visit WDW or Disneyland. I've found the parks at WDW during the first week of May to be active with some crowds, but it's always manageable. Wait times for attractions can be a walk on or up to 20 to 30 min waits for the major ones during the early afternoon. Of course you should plan to avoid attractions near the front of the park early in the morning as others are lining up for them like sheep (Spaceship Earth at Epcot for example) right as they walk in. With all that being said, the media events surrounding the 50th Anniversary/Happiest Celebration on Earth kick off that week could greatly increase crowd issues and wait times or at the very least cause some park specific issues during certain times of the day when and where the current media event is going on. We will just have to wait and see. I'm going to be there May 2 - 6 myself. As a possible indicator, I did find a couple of priority seating arrangements for dinner tougher to get than normal when I called on April 6th, but that was only for the California Grill and Ohana.