If you're seeing mirroring-related waits, check the latency of the line to the mirror, make sure that nothing's wrong, check write throughput on the mirror's log drive. The state will be synchronised (SQL's spending a long time on the inserts to ensure that), it'll only switch to synchronising if it falls way behind.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability