Installation of 9.3 with mirrored root (/ = /dev/md0) works fine.
Upgrading to 10.0 by booting off boot CD works with no problems.
Upgrading to 10.0 from within Yast2 works, but system panics on reboot.
System can be booted off installation CD, but no amount of fiddling with GRUB settings will allow the system to boot directly off the hard drive.

I booted off off of CD and modified the mkinitrd script and ran it to get more detailed output:
...
+ echo -n Waiting for device /dev/md0 to appear:
Waiting for device /dev/md0 to appear: + [ 10 -gt 0 ]
+ [ -e /dev/md0 ]
+ echo  ok
 ok
+ retval=0
+ break
+ [ -n  -a 0 -eq 1 ]
+ return 0
+ /sbin/udevinfo -q path -n md0
no record for 'md0' in database
+ path=



This seems to be the critical bit. udevinfo can't find an entry for /dev/md0, and blows the rest of the script.
A new 10.0 install with mirrored root works fine, and the above command (/sbin/udevinfo -q path -n md0) produces proper results (/block/md0). Same with a new install of 9.3 (natch).

Interestingly, on a fresh install of 10.0 with no mirrors, '/sbin/udevinfo -q path -n md0' gives the same "no record for 'md0' in database" error--even if /dev/md0 is created on the command line.