We typically visited WDW in October, but it had been getting very crowded, and we were beginning to crave some warmth over the winter instead, so we started visiting WDW in late January/early February and have done so for almost all of the last seven years. There was one year when it was certifiably cold -- not as cold as it was at home in Boston, but still cold enough to cause us to have regretted making our vacation that week. Other than that, all the rest of the times there were warm days and mildly cool nights. Even for a Northerner born-and-bred like me (and especially for a Southerner like my wife), the relief from the 2-4 feet of snow is always greatly appreciated.
So while it may not be the best weather of the year for Orlando, it's the best by comparison to home at-the-time, and that makes it our choice year-after-year.