As Team Foundation Server (TFS) becomes the source code repository for more
and more teams, SQL Server DBAs are ultimately responsible for the backup and
availability of these databases.

Sudhir Hasbe the Program Manager for Team Foundation Server has noted that
SQL Server 2005 Mirroring will provide a warm standby but

TFS will not automatically failover
. After a failover of the database
mirroring (manual or automatic) the database settings in TFS will need to be
change to point to the now Primary database server.

Update 6th Nov: Microsoft have published four draft whitepapers on Mirroring TFS with SQL Server: