I have had a sles10sp4 out-the-box install running for a long time - worked perfectly as a XEN host with several DomU's.
I now upgraded host to sles11sp2 incl. all needed patches from online update. My DomU's were backed up with dd command (from separate partitions to external disk) and restored back with dd to new linux raid1 partitions. Most seems OK, but I have a Windows XP DomU giving me headache: Shortly after bringing the DomU up (xm start) the host will crash completely - some kind of unclean forced shutdown, I am not sure what happens.
Restarting host it will recover file system from journals, similar to after a power failure. The host seems rock stable without this specific DomU.