We just went for the first time this past January. We enjoyed it a lot but it was not as warm as we'd hoped it would be. It was actually pretty cold & windy one day (50's).
BUT it was like 15 or 20 degrees at home that weekend, so in comparison it was balmy!

It hit LOW 70's one afternoon...we were staying at VWL and we went to the pool one afternoon for an hour but really, we stayed in the hot tub. It poured down rain that evening and got cold - it cut loose while DH was trying to get fast passes for something while DS and I ordered dinner...he got soaked thru even with a rain coat and was miserable - AND they were out of fast passes. There was a lot of lightening so we just decided to call it a night early and go dry off & look for Hidden Mickey's around the lodge.

The crowds were not HORRIBLE...but there were definitely a lot of people there. Not as bad as summer tho. We wore lots of layered clothes and took winter coats with zip out linings so we could adjust for the conditions of the day.
I think the worst thing crowd wise was that there were all of these Brazillian tour groups everywhere...they were large groups of like either high school or college age kids and they were singing and chanting and cheering in their language - VERY LOUD and they were all over. They were very rude and obnoxious. We would hear them coming and we'd run to either get ahead of them or we'd try to figure out where they were going and we'd go the other way. Nothing like being stuck in a line like Test Track with them yelling & screaming right next to you!

They just didn't seem to know how to be quiet. At all. Ever. And each group seemed louder than the last one.