- only works for disk devices
- requires me to figure out whether /dev/disk/by-id works for this particular sort of device
- requires me to compensate for ID string changes across udev upgrades (which have happened, though rarely), adding yet *another* source of pain to udev upgrades
- doesn't actually help with the problem described at all because the /dev/disk/by-id names are still symlinks.
/dev/backup and other such nodes are identified by whatever I see fit and wired in via hardwired udev rules; generally I use the USB device serial number and wire in the partition number explicitly. It has never broken (modulo the now-I-can't-rename-but-have-to-symlink thing).