I went from the 5th - 18th May - crowds were low, but noticeably busier in the second week. Spectacular weather, warm but not so hot that I wilted or was miserable. Perfect for water rides. I think it rained one day for about an hour, we chose Epcot for that day and just ducked inside for a bit.
We also managed to get all we wanted to do in HS within three hours, Epcot & Animal Kingdom by 3pm, and nearly everything we wanted to ride in MK in a single day. If you check a crowd calendar for best park days, make use of Fastpass and start at New Fantasyland in MK you won't struggle with crowds at all.
I was very worried about crowds but really didn't have a problem, we definitely didn't queue for longer than 30-40 minutes for anything.