We went this exact time this year with the intent to miss spring breaks too. We found that as the week passed the crowds got heavier and heavier - much more than we are used to when we travel in the fall. In fact I swore that, if possible, I'd never come in the spring again (I'll probably have to eat my words). The tail end of the trip did run into Mardi Gras however and that also brought a huge influx of people enjoying that holiday. The best part of the trip was some really great weather - not too hot, not too cool that made my husband waaay less crabby than he is in the heat of the fall. HTH!
End of February isn't bad at all but will get progressively busier into March. ESPN the Weekend is scheduled for March 2-4 at Hollywood Studios so expect sizable crowds there. Baseball spring training games begin in early March and you'll simply see a greater amount of traffic from folks heading south to get away from the winter weather.
There is a small gap, not quite a full week long, between the end of President's Week and the start of Spring Break season. That's often the week my school has off, so it is often the week I go; crowds are moderate, especially in the middle of the week.
We were there the first week of March once, and it was one of the best weeks I have ever experienced at WDW. Weather was great and crowds were very managable.
I think of mardi gras as a "minor effect" compared to P-Week---and by thins point I've done just about every permutation possible of the two over the years.