I would create a new Active Directory group and move that user into it. The reason, based on our environment here, is that we get alot of requests to create users with the same rights and permissions as another user. Simply adding those users to an existing group simplifies management enormously.
The disadvantage of using single-user logins as opposed to group-based logins is that you then have to touch each individuals account in order to make a simple change. The centralised management of users for a single purpose is something that I believe is greatly underestimated.
In situations where one user has membership in several groups (a very possible scenario), the permissions are grouped together in all situations except where an explicit DENY has been issued. Try it.....I think you will be pleasntly surprised!