AD Groups as SQL Logins and Database Users work great unless you need the User to have a default schema. In SQL 2012 the loop has been closed, but this is a 2008 forum.

@yslguru, I would look to rename them so they match the person's new name. Last name changes are pretty common and I rename Database Users and Server Logins all the time to keep up. Are you storing the Database User name in any audit tables? If the Database User name is used to maintain an audit trail then you may have a bit more to consider.