Ok, here's the deal:What does "nice weather" mean to you? If your kids want to swim January is too unpredictable. We were at WDW in February 2006 and it was way too cold for me to swim. One day we had very strong winds and highs only in the 50's.
If you are looking for low crowds March will not be the month for you, especially in 2008. Easter is early in 2008, March 23. I am guessing from President's Day on the crowds will steadily build and will reach their max from March 16-March 30. With spring breakers and the spill over from the Daytona 500 you will not catch me at a Disney from mid February until after March.
Soooooo.....as I did on your other poll, I voted for early May. We just returned from a trip from May 12-19. The grounds were beautiful with everything in bloom. Crowds were very managable, the lowest I have ever seen and I have been at WDW in February and November of recent years. And the weather was perfect. Mornings and evenings were beautiful, and mid-day was hot and just right for a swim.
Good luck deciding!
The kids DEFINITELY want to swim, but the wife is concerned with it being too HOT. My wife and I went May 28 - June 4 in 2005, and the heat was too much for her. Not that we didn't have a good time, it's just that she doesn't want to go back to Disney when it's that hot. We were actually looking forward to the Rain that would blow through on a daily basis. I love what I'm hearing about Early May, but the wife is still concerned that it will be too HOT

So basically, we're trying to find a time to go when the crowds are low, it's warm enough to swim, but not hot to the point where we have to have those little fans that squirt water.
Looking at the weather underground website, Late March and Early April meet our weather needs perfectly, Lows in the low 60s and Highs in the Upper 70s, but the Crowds are insane. January meets our low crowds need perfectly, but the weather is too unpredictable to be able to assure the kids that they'll be able to swim. I'm fine with the lows being in the low 50s and highs being in the low 70s in January, but the problem is that January is the most unpredictable Weather month in Florida, and we definitely don't want it to be in the 30s when we're there. Also, the threat of Closures/Refurbishments in January scare me
