Rated 4 out of 5 stars

Nice addon.
To (temporary) fix the problem with the white on gray selected item you could do the following.
Find the overlay.css file.

~/.mozilla/firefox/***/extensions/{9aad3da6-6c46-4ef0-9109-6df5eaaf597c}.xpi:chrome/skin/classic/style/overlay.css

And comment the line as follows:

menuitem.FirebugAutocompleter_popup_menuitem {
/* -moz-appearance: none !important; */
}