Despite stress testing the 'new' hardware a couple weeks ago, the load of actual users has brought to light a problem.  Periodically, when the system tries to write to the database, the disks have a tough time keeping up.  It appears to be something wrong with the RAID controller for those of you who know what that is.  I've set up some monitoring and am watching it closely to identify when the problem happens.  Right now, everything seems to be running well.  Knock on wood.  I'm also in the process of lining up backup hardware should this one fail entirely.