Since I switch between Linux Firefox, Windows Firefox, and Chrome, it would be nice if I could access tabs with the same shortcut everywhere. The path of least resistance turns out to be to make Linux Firefox understand Ctrl-<digit> for tab switching. So here's my first Firefox extension, which seems to do the trick:

Files currently attached to this page:

tabaccesskey.xpi4.0kB

(tested on Iceweasel 26.0)