Mobile Me Family Pack Accounts: Do Sub-Accounts have their own syncing features?
Yes a family pack allows you to create 4 additional usernames that have all the features of the main account, the only difference being that they are limited to 5gb of storage.  I upgraded to a family pack and used one of the 4 additional accounts for my girlfriend so she could use Find My iPhone (before it was free with an AppleID) she can also sync her bookmarks, dock, prefs, etc just like my account.  

The only thing I am not 100% sure is if she can also create alias email addresses like I can on my main account but I believe she can.