I'm a long time user of Mozilla, later on Firefox. Sort of. Because I've been using it mostly as Galeon - lightweight browser which uses Mozilla's renderer.
That being said it does not matter to me that much how many features Firefox has or does not have. Galeon feature set (and Feirefox renderer abilities) matters most to me. And while Galeon is something like "dead" for few years (no new features, only minor maintenance tweaks to get it running with newer Firefox releases), I have to say that my browsing needs seems to be stable for now and I'm satisfied.
But there is one big concern growing: library bundling by Firefox. It's against Fedora packaging policies, it's against what I consider good software engineering. Coupled with slower "inivation", why would I want to destabilize my whole desktop just to get slowly evolving Firefox?
So, either Firefox goes to its roots or I have to look for another browser.
Chrome is bundling forked libraries too, so out of question for me. That leave WebKit based browsers.
So, we'll see.