Xbox Live Now Has Account Migration
This will be music to the ears of any Xbox Live user who has moved from one region to another.
Major Nelson has confirmed that Xbox Live now has region migration, which basically means that if you had an Xbox Live account in the U.S. and then moved to say, Europe, you can now retain your account without having to start from scratch. That will let you keep your gamerscore, achievements, Microsoft Points and membership term intact.
Microsoft has put together a handy little guide that will take you through the process of migration your account if you need to.
You can read it here.