Update Apple ID to iCloud @me address
Does this help?

How to change the name you use for your Apple ID


At My Apple ID, click "Manage your account."
Sign in using your current Apple ID and password.
With the Name, ID, and Email Address drawer selected, click Edit next to your Apple ID.
Enter your new Apple ID in the Apple ID field. You should use your primary email address as your Apple ID. 


You can change a non-me.com address, but you cannot change a me.com address to something else.

Do you want to change what ID you use for iTunes and AppStore purchases?  


Open iTunes
Click Store
On the menu, you will see View My Account, followed by the account which is signed in.  If the account is your .me account, you are done.
You are signed in with something other than your .me account.  So, sign out.
Sign in with the .me account you want to use.  You are done.  
Repeat as appropriate on the AppStore and on all your other devices.