[dnanian]

You definitely don't want to use the Sandbox as a backup, Fred. It's a "system checkpoint" -- a safe place to "play".

So -- if you install a system update, and it's OK, you can follow the instructions to copy back with the reverse smart update as described. And this will also update any applications you've installed yourself on the Sandbox.

It's up to you where you'd like to install a manual application. If you drop it in Applications on the main drive, and you're sharing applications, the alias/symlink will point to the new version. If you replace the alias/symlink in Applications on the Sandbox, it'll be on the Sandbox only unless you copy back.

Make sense?