What am I going to lose if I move my MobileMe account to iCloud?
Apple has a fairly detailed FAQ on what will change when you convert your account, but in case you don't feel like reading through it, here's a summary: You'll keep syncing your mail, contacts, calendars, bookmarks, and notes; you'll still be able to use Back to My Mac and Find My iPhone; and though they're not supported under iCloud, you'll continue to publish your iWeb websites and photo albums in Gallery, and have access to your iDisk, until June 30, 2012.
After moving your account, however, you won't be able to sync Mac Dashboard widgets, keychains, Dock items, System Preferences, and data from third-party Mac apps that integrate with MobileMe.
I have a MobileMe family account. How can my family members and I move our accounts to iCloud?
Since iCloud is a free service, the concept of "family packs" has gone away. As such, you can move each MobileMe sub-account over to its own iCloud account by heading to me.com/move.
I have a MobileMe account and a separate Apple ID. Can I merge them into an iCloud account?
Not at this time.
Single-user setup scenarios
If you're looking to move yourself--and yourself only--over to iCloud, here are various scenarios you may run into when signing up.
You have never purchased anything from Apple (besides this brand-new device you now have in your hands). You don't know what an Apple ID is. You want to sign up for a free iCloud account: Great! You can do this one of three ways: sign up from the icloud.com website; sign up from a mobile device running iOS 5; or sign up from your computer running OS X Lion.
You have a MobileMe account you use for syncing and for purchasing items: If this MobileMe account is your only account, and you're running both iOS 5 and Lion, you can head on over to me.com/move to convert your account to iCloud.
You have a MobileMe account for syncing, and a separate Apple ID for purchases: Move your MobileMe account to iCloud.
After you've done so, you can add your Store credentials separately. On an iOS device, open up the Settings app and tap the Store menu. If you've added your iCloud account to your device, you should see those credentials logged in; log out and input the Apple ID you use for purchases. On a Mac, open iTunes and go to Store -> Sign Out, then Store -> Sign In and log in with your non-iCloud Apple ID.
You had an iTools/.Mac/MobileMe account, but stopped subscribing; you still use that mac.com/me.com address as your Apple ID for purchases: Convert your old account by going to the iCloud website and logging in with that account's credentials. You can also do this by logging into iCloud on your iOS device or Mac. (On an iOS device, go to Settings -> iCloud; on a Mac, go to System Preferences -> iCloud.)
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