All that is entailed is you must re-agree to the XBL Terms and Conditions agreement, and enter a new credit card if you used one of your parent's. Along with that comes the ability to change the Windows Live ID associated with your Live account. Doing this will allow you to associate a new Windows Live ID with your account, as well as transferring all Microsoft points over to the new account.
Lastly, for those of you with a child account and still under the age of 18, you will now have access to the Instant Messaging feature of the dashboard. Interesting, it seems like Microsoft has listened to it's scorned customers and has made good on their promises.