I don't think firefox's plight is entirely their fault - far from it. It's google's aggressive
I do know something about customer retention and it's giving them what they want, and they aren't.
Google could so anything they wanted and I wouldn't care as a Firefox customer EXCEPT that Firefox doesn't listen to us when we tell them what we want. They're trying to keep up with Chrome, failing, but that wouldn't matter if they keep up with customer requests.
See, when I worked for Lotus I heard the same arguments about Microsoft and the fact of the matter was Excel was simply a better product and the team would rather whine ME used special Windows calls they didn't have access to use instead of fixing their core, which was the issue, the Lotus 123 for Windows was dog slow compared to Excel, which had nothing to do with special Windows calls, and had all sorts of memory issues.
Basically, Lotus lost the war worrying about Microsoft instead of their customers just like Firefox is worrying about Google.
Google can be as aggressive as they want but Firefox has to be just as aggressive and make more deals to get it pre-installed on desktops and phones if possible, run some TV ads for mind share, and above all, listen to their customers!
The world is going jQuery and AJAX for all sorts of online apps, including spreadsheets and word processing online, which requires lightning hast javascript which is where Chrome shines and even MSIE got with the program and boosted their speed.
People complain about the UI changes, they ignore us because "that's the way the other browsers are doing it" which is a big fat WHO CARES! because we used Firefox because of how the UI did work.
People raised all sorts of hell and Firefox ignored them.
That's NOT how you retain customers.
Firefox simply needs to be best of breed and they're not, so they need to be what the customers want, and they were but now they're not.
I, like all the rest of us, adapted to the fugly UI changes but I find the top of the browser layout and behavior less usable than it was in previous editions.
The lack of an actual status bar I can enable, that sucks too. I don't like the little floating status at the bottom. Since the status bar is now gone, I'd prefer that little pop up status to be positionable as I'd prefer it at the top where all the other action is happening as I tend to not see what's going on down their anymore since it's not a static status bar.
Lot's of little stuff like that really bugs me, and it all piles up to the point I started using Chrome more simply because they don't have things I used to prefer that kept me in Firefox.
What really bugs me is they didn't have to remove prior UI elements, they could be optional whether it's the UI standard or not.
Silly stuff.
In the end they have one other major problem, they have no compelling killer app feature that sets them heads above the competition.
I have some ideas that I think would significantly differentiate Firefox from the rest, but I don't work there and I'm not getting paid to solve their problems ;)