Craig, Copilot Support has been made aware of this issue and is working it.  I will send you a PM with your case number.  
We have a new dual controller Compellent SAN.  Each controller has 4 iSCSI ports.  Two ports in each controller are part of a separate fault domain with a VIP.  Each fault domain is serviced by a single iSCSI switch (two total).  The switches are not connected to each other. We're running the following flavor of Ubuntu:  2.6.32-33-server #72-Ubuntu SMP Fri Jul 29 21:21:55 UTC 2011 x86_64 GNU/Linux  I have installed multipath-tools and open-iscsi. I can successfully connect to the volumes that Compellent is presenting to and get the I/O performance that I would expect. I can run iftop and see that traffic is being balanced evenly between my two Intel NICs.  The problem comes during simulated failovers.  If I reboot one of the iSCSI switches and bring down that fault domain, the Linux server stops sending data on the other path.  It just sits there until the switch comes back up and then both physical paths come alive.  That can take up to 60 seconds and that is a looooong time for I/O to be paused on a server. It seems that I've tried every combination of settings in multipathd.conf and all of them experience this issue.  An example:
Multipathing problem on Ubuntu Lucid