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...

There's a good reason "Do Not Track" is unchecked by default. If it was checked by default, then advertisers would have the perfect excuse to ignore it: "oh, that's not really the user's preference, they're just sending that header because their browser sends it by default; let's go ahead and track them."

By making it opt-in, we ensure that a site receiving a do-not-track header knows for sure that it represents an active choice on the part of the user.

You may remember that IE was going to turn it on by default. But then Mozilla and the rest of the do-not-track collaborators explained this principle to them and they went back to off-by-default.

The third-party cookie thing, though, I don't have a good explanation for. When I worked at Mozilla I spent a lot of time trying to convince people that we should block third-party cookies by default. (Especially after I started working on Collusion and saw how prevalent they are.) I kept getting the same response: "We can't block 3rd party cookies, it would break the web."

I don't agree with this, obviously. Before pop-up-blocking became the norm in all browsers, you could have made the argument that pop-up-blocking would "break the web" too. I believe 3rd party cookies are a giant security hole, and breaking sites that use them would be a small price to pay for closing it.

But, I couldn't convince Mozilla of that. It's one of the reasons I decided to leave.

> Are curved tabs really better than rectangular ones?

IIRC from the UI design talk where the new "Australis" redesign was introduced internally, the motivation behind the curved tab redesign was to look "friendlier" and more "organic".

One thing the Australis redesign does which I do think is important is that it finally provides a consistent location for add-ons to add buttons. (The status bar used to be this, but it was hidden in Firefox 4 to recover screen space for content.)

> 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.

There's a good reason "Do Not Track" is unchecked by default. If it was checked by default, then advertisers would have the perfect excuse to ignore it: "oh, that's not really the user's preference, they're just sending that header because their browser sends it by default; let's go ahead and track them."

By making it opt-in, we ensure that a site receiving a do-not-track header knows for sure that it represents an active choice on the part of the user.

You may remember that IE was going to turn it on by default. But then Mozilla and the rest of the do-not-track collaborators explained this principle to them and they went back to off-by-default.

The third-party cookie thing, though, I don't have a good explanation for. When I worked at Mozilla I spent a lot of time trying to convince people that we should block third-party cookies by default. (Especially after I started working on Collusion and saw how prevalent they are.) I kept getting the same response: "We can't block 3rd party cookies, it would break the web."

I don't agree with this, obviously. Before pop-up-blocking became the norm in all browsers, you could have made the argument that pop-up-blocking would "break the web" too. I believe 3rd party cookies are a giant security hole, and breaking sites that use them would be a small price to pay for closing it.

But, I couldn't convince Mozilla of that. It's one of the reasons I decided to leave.

> Are curved tabs really better than rectangular ones? IIRC from the UI design talk where the new "Australis" redesign was introduced internally, the motivation behind the curved tab redesign was to look "friendlier" and more "organic".

One thing the Australis redesign does which I do think is important is that it finally provides a consistent location for add-ons to add buttons. (The status bar used to be this, but it was hidden in Firefox 4 to recover screen space for content.)

I know that this reply was in the context of Web/Browser/Desktop, however, I deal on a daily basis with some fairly clunky business applications that have pretty gungy UIs (think Visual Basic circa 2000 with lots and lots of tree controls and combo boxes).

Another more specialised business application has had a recent 'face lift' and my colleagues are using it much less because they find it hard to find things that used to be easy.

I know my way round the screens, and I know the shortcuts. I'm dreading a 're-design' of the one I use.

As regards the Windows UI, Windows 7 and Vista were different from XP which was different from Win2k which was ... The introduction of Glass, in particular, caused a lot of frustration for users that were upgrading from XP. Drivers were broken, their applications were borked, etc. Windows 7 fixed all of those problems, but a number of companies have not upgraded from XP because they don't want to deal with re-training their users.

In many ways, like Vista is to the Windows brand what the Rapid Release Process is to the Firefox brand. Both ideas caused mass defections to the competition. The jury is still out on how users will react to Metro. The dual-desktop story has two problems: the switch between the Classic and Metro desktops is not very intuitive; people are going to miss the Start Button. I think click-based heat maps should be "a" factor in making UI decisions; not "the" factor in such decisions!

Here are my closing thoughts on why a UI change should be as non-intrusive as possible. In my experience, people hate software because it has a way of making them feel stupid. The reason to be careful with changing the UI and/or removing features is that there is a good chance that the changes will people will feel stupid all over again. This is an invitation for defection to the competition.

These things have not been around long enough for "the test of time" to apply.

I think Windows interface has withstood the test of time pretty well. The basic UX paradigm is essentially unchanged from Windows 95 with whatever that followed basically being tweaks rather than big changes.

The rule for what ends up in the task bar also is incomprehensible for mortals. For awhile, every new release of Office managed to introduce a new variation (yes, Word is MDI, but all its windows show up separately being one variation)

I guess that, if you ask users about these features, they will just say "yes, sometimes it does that".

I find it takes a bit of time to find where functions have moved on Office 2010, and I seem to be taking a long time to internalise the 'logic' for finding less used functions. Probably all those years on Office old style.