Impressive as Heck, but it ain't VIM Rated 3 out of 5 stars
Interesting, impressive, a formidable amount of development and work. But it ain't VIM.
I use VIM on a daily basis. But when I tried to use Pentadactyl to browse, I spent virtually all my time in the add-on's Help files.
The underlying idea of Pentadactyl is interesting: Navigate Web pages with VIM commands. But the problem is that there are so many non-VIM commands and options that need to be learned before you can then use a handful of actual VIM commands to move around a bit. What might have made Pentadactyl work better was to use a GVIM approach so that users could incrementally learn Pentadactyl's unique commands and so ease in to more sophisticated usage.
Pentadactyl was fun to play with and explore, but in the end I needed to disable / uninstall it so I could actually use Firefox to view Web pages…