It looks to me like Pentadactyl hasn't had an update on addons.mozilla.org since over a year ago, while the "other side" of the political fork, Vimperator, was updated just under 4 weeks ago. I use Vimperator on Nightly with very few perceived bugs (nonzero, but that comes with the Nightly territory).

In my mind, the quicker iteration on features and improved code quality that came from rapid releases is well worth breaking a year-old addon, especially one as invasive into the browser as Vimperator.

Addons written with the Add-on SDK (aka Jetpack) are also much more stable across versions, though they're not the browser-transforming beasts that Vimperator is.

I don't really like web browsers as a platform, but I don't think restricting the pace that new features are released is productive.