I'm actually not, and one reason is because I've seen over the years how extension authors have to keep up with the churn constantly breaking things, and that's not a pool I want to wade into. I'm amazed that, e.g. the Pentadactyl authors have the time and patience to do so.

So, if this new API stabilizes things long-term, that's fantastic. I would love to have extensions that never break again.

But forgive me for being skeptical, because with the CADT-style development models ruling the world nowadays, what usually happens is, the old API is deprecated and dumped before the new one has feature parity, leaving authors and users hanging. And with Mozilla's trend of imitating Chrome, this seems even more likely.

I can hear the cries now of, "The old API is too hard to maintain, so we're removing it in Firefox 72. We hope to reach approximate feature parity by Firefox 84, but we do not plan to reimplement all features in the new API. Regrettably, this will prevent some addons from being ported to the new API," with the implied, "But 'no one' [compared to the number of users on the Internet] was using those addons anyway, so who cares." And cue me switching browsers.

Please prove me wrong. :)