RE: always put Customizations in `custom-file', never in `user-init-file'

[Drew Adams]

> > Be very careful.  In particular, the natural idea of migrating by
> > loading the init file and using Custom to save its internal state to a
> > custom-file caused no end of pain to users when it was implemented in
> > XEmacs.  If there is any error in the init file, you can lose all
> > customizations.
>
> Then it might be best to avoid automatic migration, but to give a
> command to migrate custom data to custom-file.

I don't see the problem, if it's understood that `custom-file' would not be
loaded automatically, but only when (where) the user requests via (load-file
custom-file).