1. Will your email aliases also transfer over? I use 4 alias email accounts and 1 main account.
2. Is "Documents in the cloud" the same thing as iDisk? I currently use iDisk.
Those are both good questions.
For number 1, reading this page from Apple indicates that they haven't answered this question yet. I think the me.com to icloud.com transition will be fleshed out as things go forward, maybe this is one item that's up in the air. My bet is that your aliases will be transferred just as your main account will.
For number 2, I think this refers explicitly to auto-syncing of iWork documents, Apple hasn't alluded to DropBox-like (that is old iDisk-like) straight file syncing. They might add that functionality in, too, but it seems most of the files will tie in directly with apps.