Rated 4 out of 5 stars
Now that the key combination (control + shift + s) is editable (in about:config under 'extensions.sitelauncher.shortcutThisPage.key') my nasty rating has disapearde with my moaning. So : the concept of this extension is simple and great, simple like all intelligent inventions. I'd bet it is to become one of those reference extensions.
By the way, concerning Firefox key configuration, I've discovered a neat little extension called... keyconfig, not available (?) on mozilla, but downloadable here : http://mozilla.dorando.at/ , works great.