My sister (heidispidi on here), niece and I went in Jan 2011' I think dates were 7th to 15th. The first couple of days were pretty cold, especially at night, e.g. While watching Fantasmic we needed jackets, hats and gloves. Us adults froze while watching the crazy child swimming the hotel pool! But by the end it had warmed up a bit and we were in t-shirts. Similar to Sydney winter weather I'd say.
Crowds were almost non-existent, we had no or 5 minute waits on almost everything. We even got to go on Splash Mountain a couple of times without getting off. There were some refurbs happening and shows only on the weekends but the lack of crowds more than made up for it. And the day we went to Universal it was like a ghost town, no wait for anything.