Well, I think there's some hope/expectation that Samsung will release the Gingerbread file necessary to Odin back to that directly, rather than having to Odin back to Froyo and then update to Gingerbread. Until that happens though, I guess you'd have to use something like the nandroid backup from custom recovery to get back to rooted stock. Of course, you'd have to have made a backup from rooted stock in order to be able to do that. If you don't, then you could go through the process of Odin to Froyo, update to Gingerbread, and root once in order to run a nandroid backup on just plain rooted stock, then you'd have it for future use -- you shouldn't have to do that process again, just use the backup. I think restoring nandroid backups is pretty straightforward, especially if all the ROMs you're using have the same base (e.g., EI22), but I'm pretty new to rooting, so perhaps someone else can provide more information. Paul627g's post indicates that the file system may play a role here, so I guess you'll have to check on that before restoring a backup. I don't know much about that. I'm still just on rooted stock and haven't tried to restore any backups yet (no need to). I hope this is of some help though.