Firefox 4.0 was not a feature release. It was a major release that included changes in the core.
Yet another arbitrary distinction... especially when most people here complain that 4.0 should actually be called 3.7.
You just showed that version numbers aren't just a number but carry meaning with them. Mozilla using them arbitrarily distorts their meaning, and this is what people are complaining about.
They don't carry meaning other than what we assign to them. What I showed is that they broke their own rules before, in a small way, pointing out the inconsistency does not mean that I think those "rules" are important. Are they doing it arbitrarily now? Nope, just differently. Bugfixes etc: small number, features added and major functionality changes: first number. It's not confusing to me, nor is the old system. And I don't care if a user says he has a problem on 4.3.5 or 7.0. The only thing that I find annoying about the change in version numbers is the addons needlessly expiring, but that situation already seems to be improving. How those numbers increase isn't very important, as long as we have an easy way of determining which is which. Their removing the number from the about box does have me worried though.
Now, you have no clue if 7 represents a major change or just a bugfix without actually testing it.
Really? What about 5.0.1 and 4.0.1? Bugfix releases still can and do happen. 7 is a feature release, as were 6, 5 and 4 before it. Perhaps the features added aren't alway major news or huge visible changes, I agree. But at least they're coming available much quicker now and can be refined sooner as well.
Hence, frustration for developers.
As a web developer, I am not frustrated by the jump in version numbers. It is, after all, just a number. If anything, it makes it easier to know when new functionality becomes available, even if it comes in bite-sized chunks, rather than wondering whether a point release is just a collection of bugfixes or actually expands functionality. If anything, I thought that they shouldn't have done the out-of-process plugins in the small numerical step from 3.6.3 to 3.6.4... that alone warranted calling it 3.7, imho.
...so this update does not turn off the feature entirely. For example, it does not impact "shiny media" such as CDs or DVDs that contain Autorun files.
I for one think this is a sensible thing to do.