I like this plugin! In the field, I realized I (and possibly other people) could use a feature, that seems not to be implemented yet – I needed to define title including the separator part (specifically: to remove that part).
Certainly only some templates are using wp_title in a way that you could set the whole title from the one field - but in cases, when typical bloginfo-name part is part of the separator parameter, there is a filter before outputting wp_title string (so you could optionally remove separator part by simple replacement function)…
Surely needs some more thinking. :-)