[frank2]

>As to your last point, you can always fire up a new Emacs process and do your highly experimental customization there

I guess I didn't feel confident in my ability to adhere to that policy (of making changes only to the secondary Emacs process), so what I do is keep a backup of my Elisp code with the result that

   emacs -q -l <path to backup init file>

always opens a process usable by me.

[ledauphin]

i commit all of my Emacs config to git and use version control, so in theory i can just git checkout abcdef1234 and I'm back up and running.