Be warned, there's a chance that the world may not load at all. It's a very buggy snapshot. So far, I find worlds with less blocks to render less in danger of this bug. (e.g. superflat worlds, having very few blocks to render except the first five or so levels)
Well, time to bump this!
MTM and I never did get that Co-Op Let's Play series started, but with the integration of Minecraft Singleplayer and Minecraft Multiplayer, that may be possible again!

Also, books can be crafted and written in without the need for mods.

Awesome.
Actually, no, they're not being integrated into each other. Rather, single player is just being made much more like multiplayer, in that your computer becomes a local server for the singleplayer worlds. Multiplayer is similar to that, but involves other people being able to connect to you. They're being made similar to each other, not being made the same thing.
I was under the impression that the only difference between a single player world and a multiplayer one was whether or not you were playing in Multiplayer mode; that is, a simple bit that indicates whether or not you're letting other people play with you. You know, like how the xbox live version does it.