For those of you who have the following setup:
1. @me.com for Sync services (i.e. Mobile Me acct)
2. @domain.com for iTunes acct/Apple ID (i.e. Gmail)
If you do not use your @me.com as your primary email but do use Mobile Me for sync services I would suggest to use your @domain.com to setup iCloud and keep your Mobile Me acct separate for now.
Later on we will find out weather we will be able to merge our @me.com email addresses into iCloud or if we close our Mobile Me acct we can reaquire our @me.com email address through activating the mail portion of the iCloud control panel.
That is the best case scenario at the moment. However, please note, this only applies if you do not use your @me.com email address as a primary email.
As per Apple FAQ the ideal situation is to have one email address for Apple ID/iCloud.
I want to keep mobile me separate for now because my mac at work is still running SL and I need MM for calendar syncing. So - if I move iTunes ID over now (I want to check out iCloud) will I still be able to move MM over later - when I get Lion at work?