Hi, We just got back from our trip this year March 8-16. The weather was absolutley beautiful. Mid 80's and sunny everyday, only one quick rainstorm.
As for the crowds, I thought they were a little heavy. The parks were very crowded by mid day. We were able to manage by going early and maximizing our fast pass. But I did think that walking though the parks was tough at times because of the heavy crowds. There also seemed to be a lot of teenagers. I think many schools had senior class trips at that time.
Also, make sure you have PS's for dining. The restaurants seemed crowed as well.