Rated 5 out of 5 stars

IIRC, I installed this first when it just appeared (not knowing if it was good, but to try what was planned for the next version of Firefox), and I am still using it.

Without it, I would have to press Ctrl+Shift+Tab all the time. That said, I now forget about the very useful Ctrl+Shift+Tab feature of this add-on, and use Panorama instead sometimes.