User Interface Design and Firefox

There is an interesting article on rapid releases in Firefox over on hackernews. I posted my thoughts on the UI changes in Firefox since the 4.0 release as a comment on that story. Here is the text of the comment:

Very few user interfaces have withstood the test of time. There are notable exceptions, of course - the iOS UI, uTorrent, and the Chrome browser immediately come to mind. Other applications and operating systems have continued to evolve their user interface over 18-24 months. In some cases, the evolution is necessary for the sake of usability. Take Android for instance: The UI update in ICS dramatically enhanced usability.
In my experience, the designers of unchanged interfaces put a lot of thought into almost every interaction a user could have with their application/operating system. Armed with the use-cases, the designers invested time and effort in creating the core UI "right", and determined a seamless way to make incremental updates. Chrome and iOS are, again, perfect examples of this concept in action. Firefox, Windows (minus Metro), and earlier releases of Android - not so much.

Firefox's UI changed radically in version 4. A good number of users revolted and there was uproar about the theme refresh, but most of the users that stuck around got used to the changes. That they are changing the UI again, only 24 months after the fact, does not reflect very well on the design philosophy behind the 4.0 refresh. Lots of questions come to mind - Did the designers not do adequate research during 4.0? Was the development time-frame too short? Was 4.0 just an interim solution to what they perceived a bigger problem? Are curved tabs really better than rectangular ones? Do I get back a lot of screen real estate? Is this a case of Not-Designed-By-Me syndrome?...

I continue to use Firefox today, partially because I know my way around the application so well but mostly because I trust that Mozilla values my privacy. I do think that they go half the distance sometimes with their privacy measures - "Do Not Track" is unchecked by default, and Firefox accepts and keeps "Third Party Cookies" until they expire. In these specific cases, I understand that these are measures taken to ensure they can keep the lights on at their headquarters. With the impending changes to the UI, I will be using the app only on the basis of my trust in Mozilla. And we all know that trust is a tenuous thing to hang by...