Rated 5 out of 5 stars
I wrote the author a couple of days ago to ask if he would bump up the maxversion, since I had been using the extension without problems in various Firefox 4 betas. I was also bothered by the fact that the window always appeared in the top left corner of the screen. Imagine my surprise when he fixed both issues that same day!
As for the extension itself, it does exactly what it says. It's one of those common-sense features that should have been included in Firefox in the first place.