Why do you feel rapid development is a good thing?
What is the pros in rapid development? I am scared to update because I am afraid my ad-dons wont work.... Shouldn't you at least allow a way to easily rollback to another version? Just Saying could have picked a better time to be messing around. Chrome is already taking many users, why don't you see this? This is no angry rant I use Firefox faithfully for as long as I could remember, "when it felt good to use the best browser". Now I feel like the loser kid getting picked on in school. What happened to "User Centered Design"? Where did my speed go? Please don't make me change Chrome to my default browser.
ప్రత్యుత్తరాలన్నీ (1)
A few versions ago, Firefox stopped disabling add-ons that didn't list the new version. There still are feature/function/security/interface changes that sometimes break add-ons, but the whole number version thing shouldn't be a problem any longer.
As for the advantages, the whole point of this new method of releasing is to get new features to users as quickly as possible instead of saving them up for long periods of time.
Now, about speed, which versions are you comparing?