For web application developers this attitude is unreasonable. You can't possibly test your development code and every previous release against every browser variant every night. The other point you seemed to miss is that Mozilla's bug BROKE CODE THAT WORKED WHEN IT WAS RELEASED.
The point of this whole discussion isn't that there was some new release, but that Mozilla was actually nimble enough to respond as quickly as they did.
You keep trying to turn this into some ugly flame war over who has better development practices. Take a valium.
"Anyone attempting to generate random numbers by deterministic means is, of course, living in a state of sin." -- John Von Neumann