For the past 3 years, I have gone during the week in February prior to Presidents Day weekend and have been pleased with prices, weather and crowds. You will need to time your trip to leave WDW no later than the Thursday before Pres Day, since that's when the resort rates go up (and presumably the crowds start building). The Jan-Feb "Value Season" dates have pretty much the lowest resort rates of the year, and you'll probably be able to get some sort of discount (unless you're staying at an AOA Mermaid room - or POFQ

).
Now, for 2016, Mardi Gras is February 9, so that rather complicates matters. Although I will say, I was there for Mardi Gras in 2013 (when it was similarly early), and I actually enjoyed it. The crowds were a bit bigger, but not really a problem. I suspect Mardi Gras is a bigger problem crowd wise when it coincides with Pres Day week (as it does this year) or the start of Spring Break season that follows.
Average highs are in the low 70s. I had a couple of VERY cold mornings in 2012 and a couple of cool, drizzly days in 2014, but the weather when I was there was mostly beautiful.
For me, the biggest negatives about February are the fact that Splash Mtn is usually closed (except for this year, of course, when I moved my trip to April), and you may have to worry about winter travel weather depending on where you're coming from.