And... Did it work?
I very much doubt it will work.
We have not been able to edit MobileMe accounts like Aliases since June.
I tried - no banana.
So, what I did is used the AppleID that has the most purchased music attached to it (and is the one I am most commonly on the iTunes store) and used that for iCloud.
When you are setting up iCloud on your Mac you can set up the free synced iCloud email account and I will start using that from now on. The contacts and calendars will sync to the new account anyway, so no probs there and I mostly used Flickr and Facebook for photos - so Gallery wasn't a big loss for me.
Only problem is the MobileMe mail, which I have a lot of. I will keep using it until they turn it off as it still syncs fine, but I hope Apple will do something great with it.. as in merge the accounts!!