Hi, we were at WDW 4/15-4/23. We went during our Massachusetts April vacation week and saw many folks with Red Sox clothing; lots of NE people! As noted by the earlier posters, much of NE and some of NY usually has the 3rd week of April off each year. However, there is often some variation in different areas. Next year will be interesting with Easter so late; not even sure yet what week we will have off for school.
The parks were crowded, but ok if you went early and used fastpasses. By lunchtime MK was pretty unbearable and we tended to leave for breaks. I found Tomorrowland particularly crowded. MK was also pretty good in the evenings; we walked on rides such as Pirates and HM by 8:30 pm or so. Epcot never seems as crowded, but were were not able to get on TT; too late for fastpasses and we did not want to wait 70 minutes! AK was fine in the morning, but VERY crowded by noon. It is also a very hot park when crowded. Fastpasses are the only way to do the safari without a long wait, unless you get there early!
We had PS for all sit-down meals and heard many folks without PS being turned away. However, friends who were down the same week were able to make PS the morning of each meal....not always the exact places and times they wanted, but they were flexable. As for the weather, perfect!! As the other posters said, a bit cool the first couple of days, but still better than home (ha ha...it is only 50 degrees here now). Otherwise, low 80s, no humidity, and no rain. We were actually in the airplane waiting to take off when the rain on the 23rd hit...so lucky. We have gone this same week in the past and had equally good weather.
Overall, I think the 3rd week in April is a good time to go, but I would be wary about next year with Easter so late. Have fun planning!!