Does what it says, and looks good!
Only issue: You have to add the https-version of Wikipedia to its included pages manually.
Doing [Ctrl+Alt+f] to show the side bars, when hiding them again, the article does not stretch to widescreen, it stays at the left side of my full screen browser. To get the proper full screen view of "only the" Article Mode, you´ll need to reload the page, but even if you don´t the script does what it says, Article Mode. (Firefox 7.0.1 and GreaseMonkey up to date).