For starters, anyone with a .Mac subscription will be automatically upgraded to MobileMe and see their iDisk storage doubled from 10GB to 20GB at no additional cost -- though Apple warns that it may take up to 10 days before the additional space is reflected for all users. An email will be sent out to all .Mac subscribers ahead of the service change.
Once upgraded, users will be under no obligation to stop using their .Mac email address or their .Mac email aliases, both of which will continue to function indefinitely, as will .Mac iChat login IDs. In addition to their mac.com email address, users will also get an address at me.com with the same username and an iChat ID at me.com with the same user name.
Similarly, .Mac website URLs and Web Galleries URLs will continue to function as they do today, but will also be accessible from me.com. For example, both web.mac.com/john_smith/ and web.me.com/john_smith/ will both point to the same web directory. Users who have their own personal domain name pointing to their .Mac web directory will also not need to make any changes.
Emails stored on .Mac, as well as files on a .Mac iDisk and Backups to a .Mac iDisk will all be accessible from MobileMe and continue to function as they do today. Some other features, however, will be discontinued such as iCards, .Mac slides, and support for Mac OS X 10.3 Panther sync.
Apple will also discontinue Web access to bookmarks on June 30, 2008, after which users will no longer be able to access or update their bookmarks at .Mac. To avoid losing any existing .Mac Bookmarks, Apple recommends that .Mac users sync them with Safari on a Mac before June 30.
Bookmark sync between Macs and/or PCs will not be discontinued, as MobileMe will continue to sync bookmarks across computers as well as push them to the iPhone and iPod touch.
On a Mac, MobileMe will require the latest versions of Mac OS X 10.5 Leopard or Mac OS X 10.4 Tiger, and either Safari 3 or Firefox 2. Windows PCs will be able to access MobileMe from Safari 3, Firefox 2 or Internet Explorer 7. iPhone features will require iPhone Software 2.0.
Additional information is available via Apple's .Mac Transition Overview and the MobileMe Guided Tour. Prospective subscribers can also sign up to receive a notification email when the MobileMe service goes live.
Update: Readers in the AppleInsider forums ask if they can purchase the current editions of .Mac at the discount price of $69.99 ($124.99 for the Family Pack) from Amazon.com and then have their account upgraded to MobileMe.
Apple say, "Yes. Just go to www.mac.com/activate and enter your code to get started. Your account will be automatically upgraded to MobileMe when it becomes available."