I've been searching for a snow or a mushroom biome for about six hours in 1.9pre (in a test world) and still haven't found anything.
The new Nether content is great, it makes the place much more interesting, but there's still no extra reward from it. There's ghast tears, blaze rods and nether wart, but none of those things have a use yet. Hopefully we wont be waiting a year for them to have a use like we did with slime balls. Also, I hope they add a way to manufacture nether brick using netherrack.