The Halloween-update is out..
I've just given it a go. I've heard there's some errors with the Nether (Hell) realm, so I decided to go looking for new biomes until that is sorted out. I headed south in a boat, and the first plots of new land generated had snow on them!
So I walked around, did some exploring and found this:
Lava flowing into an ice-lake. Aww yeah.
A flower and some grass growing under the ice.
I also did something amazingly stupid (surprise, surprise); I broke some of the ice, dived in, got lost in the darkness, couldn't find the hole out, tried to break the ice above me, but slipped away whenever I touched it. Luckily, I got out just in time, but I still can't believe how dumb I was to do that. There's some horrendous chunk errors where the newly generated land meets the old land from my save, but once I got past that transition point, things look much smoother.
I can't wait for biomes to get region-specific attributes, killer snowmen and penguins in snow regions would be awesome, but for now it's nice to just explore lands that aren't all green and brown. For now, I think I'll build a shack on a frozen lake and go ice fishing.