We've gone at that time several times, and I don't think it's too bad considering it's park of the peak season. We went the first week of March three times, but I will say that the airport was a lot more crowded on the way home, so obviously it starts picking up.
We walked onto most rides, etc. Never had to wait much for anything. We're pretty laid back about that stuff though, so I may not be the best to answer that. But it's definitely not as bad as how people describe the summer and holidays to be.
We also stayed offsite so we only dealt with this stuff at the parks. Even the restaurants offsite and stuff weren't too bad during the weeknights. So, my guess is that things were similar onsite.
Have fun...it's a good time of year to go. Cool in the morning, beautiful in the afternoon and not too hot. And definitely warm enough to swim most days...especially in the heated pools in the sun!
The first time we went was Thanksgiving week 2006, and it was freezing...I wore my winter jacket while we were there, it was also pretty crowded. The second time we went was August 2007 for free dining and it was hotter then hot...and the crowds were decent sized...I'm hoping for nice (70s weather) and not to crowded...but I can deal with just about anything as long as I'm in Disney World!