Puntuado con 5 de 5 estrellas
Update ... Starting afresh with a clean version of IceDragon portable, I've found that the problem persists with the icon/button not showing.
However, I discovered that I can easily make it reappear by just disabling then re-enabling the add-on. So it's still very usable, especially as the disabling/re-enabling doesn't require a browser restart.
Puntuado con 4 de 5 estrellas
This looks realy useful to me, but after installation I have no toolbar button and no way to access the toggle.
(W7 x64, IceDragon v21)
By default, Firefox installs this add-on into the add-on bar (Firefox -> Options -> Add-on Bar) from where you need to drag it into the toolbar in "Customize" mode.