Another vote for May. Lovely time to go, great weather, manageable crowds and lovely long, light evenings. Best holiday we had at WDW was in May.
Earliest we did was February a couple of years back...it got waaaaaaaaaay cold and not a time of year I would consider going again, unless we had no choice. Parks dont open very long, gets dark early, water parks closed, lots of rides in refurb...you get the picture!! GO MAY!!!
Allie