One of my few truly essential add-ons. Rated 5 out of 5 stars
I love it! tIf you like Vim then this extension should really appeal to you; otherwise you might want to just skip it or play around with Vim a bit first to get a feel for whether you even want to attempt to learn it. I'd been trying to relearn Vim since my time with it about 25 years ago. Pentadactyl was both natural for me to learn to use with the added benefit of fast-forwarding my Vim skills.
This extension is the only one that might cause me to revert to a previous version of Firefox. That said, it's been quite a few releases since I've had to revert; most of my experience has been that if I force enable Pentadactyl that any problems are few or non-existent and an updated release isn't usually long off.
Besides, I'll try out any add-on with a picture of Mahler on the front logo.