We just got back on Feb. 16, we were there from Feb. 9th. We made sure to go BEFORE president's week. The first Saturday we went to MK and it was pretty darn crowded. However, we did get there right at open so the first hour or two was very nice. Other than that, I didn't think the crowds were bad at ALL, and DH and I are definitely not crowd people.
I think the longest we waited for a ride was 15-20 minutes. We rode Buzz three times in a row, POC twice on different days and no wait. Our longest waits were Dumbo (very slow loading ride), Turtle Talk, Rockn Roller Coaster, and Living w/ the Land. Those just are summed up to bad timing, and even so the wait wasn't bad.
One day we got to Epcot about noon and it was practically empty in the World Showcase, we felt like we almost had the place to ourselves!
The weather was in the 60's for the most part, a few days it broke 70. We had a cold snap for a couple days and they had record breaking lows at nite....but during the day it would still warm up a little bit.
As long as you don't have your heart set on water parks, I would HIGHLY recommend Feb.!!! We swam at the pool at our resort the last day and it was great.....it was only 55 when we got in but it was heated - and in the short time we were out there, the sun came out full force and warmed things up nicely.

Just pack sensibly....bring things you can easily layer, like a sweatshirt over a t-shirt or something like that. GO FOR IT!!!