If it doesn't pan out, I may just go with my "data" (docs, photo and music libraries) on the SSD, and put the Users back where they "belong." Then I'll just make sure I'm tidy with my desktop and move things off into the Documents folder before the desktop (on the SSD) gets too full.
I think this problem is occurring when an application tries to access the user directory when the RAID hasn't come up yet for the system -- whenever OS X fails to find the user directory where it expects it, it creates a new one (like the behavior when users changed the name of their home directory in previous versions of OS X).
Normally, in Unix, one might go a step further and establish a
mount point using fstab for the /users directory. This I guess would be lower level, and it would prevent the problem, because even if OS X were to try to create a new user in /users, /users still always would point to the alternate drive.
But
it seems that fstab is deprecated in Leopard and people are having trouble doing this with the automounter.
FWIW, not in the context of an SSD boot drive, but in the context of Filevault, I didn't want a 40GB filevault file that contained encrypted versions of MP3s and stuff like that, so I just moved my large directories that didn't contain sensitive information like the music and so on outside the encrypted folder, and this
did work fine. I'd figure that, if you could move all your document folders as well as your music and so on off the SSD in this way, your home folder would actually be quite small and pose no real issue for the SSD?