We tend to visit in late Jan or early Dec, however we did go to WDW for a week over Mother's Day this year. It was our first May trip, and there was so much about it that we loved! The crowds were quite low, with the exception of the MK on spectro night. The MK was the most crowded we have ever seen it that night, and we quickly hopped to Epcot to get away from the madness. Epcot was virtually empty, so I think everyone was at the MK! As others have mentioned, the parks tend to close earlier in early May, however we felt we were able to see everything we wanted to, and we enjoyed our evenings away from the parks (Cirque, the Boardwalk, mini golf, etc). Over Mother's Day weekend, our resort (AKL) was very crowded. The resort did quiet down the day after Mother's Day, however. Also, I will note that it was extremely hot and humid while we were there, and it slowed us down a bit. It did not rain but we melted from the heat/humidity. According to those we spoke with while there, the weather was unseasonably warm this past May. I think, usually, the humidity is not so bad in early May. We would not hesitate to go in early May again!