Sorry if this was posted already but I saw this on Reddit
http://www.reddit.com/r/Minecraft/comments/kb87s/20000x20000_world_in_18_this_time_image_scaled_10/
it's a
20,000 x 20,000 map of a 1.8 generated world compared to a
world generated a few months ago. No, there's no snowy biomes but Jeb or Notch mentioned somewhere they weren't testing them so it's most likely they're just not in the leaked build we have but will be in the final version that releases (hopefully).
I'm not sure how up-to-date the leaked 1.8 build is but Notch tweeted a few days ago:
Fixed the biome code so villages only spawn on flat areas. Nice.
I finally generated a really cool world and found an awesome mountain biome. Built a cool house on the edge overlooking the water and now I find if I use the furnace my game crashes. Basically whenever the furnace entity updates so when it starts cooking and when it stops. Really annoying, wish I could play the real version of the update - don't really want to go back to the old world gen now.