So, I sat down to check out the 1.9 pre-release, and for once, my seed phrase actually produced results I wanted, plus a bit more. The seed "MushroomMayhem" or 256662051 produces a rather interesting island world.
I found myself on a rather interesting island, with balancing spires, other interesting features, and lots of rock, and an accessible, fairly vertical shaft that goes down a ways. It's basically a quarry island, with lots of coal, stone, a tree or two, and some red mushrooms, plenty to get started for survival. I couldn't see much to the north, but there's a giant pillar island that rises out of the water to the south, and a good size pine forest island to the south west. And then, I decided to sail south from the pine island. After several minutes, I struck gold, or rather, mushrooms... lots and lots of mushrooms. On to the pictures!
The island you start on. Some red mushrooms grow on the far left side
The Spire island to the south
Then, after finding the mushroom island further south, I crested a ridge, and saw this:
Shroom Cows Everywhere!
Anyway, this seed is worth checking out!
[Edit] Coordinates for the shroom island: x 748, y 82, z 666
Heh, you're all welcome. And yes, I was using a texture pack, so the new mushroom biome grass showed up as solid grey blocks. I'm still amazed at the number of cows I found there. There are close to forty across both those screenshots.
@firetempest: that seed looks pretty crazy, especially since it's connected to another biome.