Firefox GUI innovations...
Are none of such a thing. In fact I feel very pissed when people call reinventing the wheel "innovation".
Their "innovation" is nothing more than a bunch of contrived changes to the GUI for the sake of change, no one asked for any gui change because the GUI was OK.
What people has been complaining for ages and with no end in sight is memory consumption, slow start-ups and general performance degradation.
And what does Mozilla do about those dreadful issues almost every single user has? NOTHING!, let me repeat, N-O-T-H-I-N-G.
Instead they choose to change the GUI almost entirely, waste time providing us with an over-engineering tab grouping feature that doesn't work well, and remove useful features like the status bar. (And those are not the biggest felonies, but not the only ones, gratuitous ad-don breaking I'm talking to you!!!)
The funny thing about the grouping thing is that no one "gets it" or find it useful, and what does Mozilla do? they put a bloody video on the next beta so people will at last understand what the thing is for, assuming not that maybe the feature is not well designed/devised, but that their user base are all morons who can not make sense of their greatest invention.
Sooner or later a proper Adblock is going to be released for another browser, and that day FF will lose a big chunk of users straight away. In my case the only reason I'm using Firefox is "adblock" and occasionally "firebug".