[morinted]

The side-tabs don't have any hierarchy, but already you can fit many more tabs and have them visible at once than the tabs-on-top.

I think the main thing that keeps tree tabs from happening is that it's an advanced concept for the everyday internet surfer, which is what Firefox has been trying to appeal to more and more lately.

[reitanqild]

The thing I think both Mozilla (it seems a few of you hang around here now) as well as others should understand is making certain feature switches available for end users.

Just because something isn't for everyone doesn't mean you can make a browser for everyone by removing said feature for everyone.

This should be obvious but thanks to what seems to be a certain kind of ux designers we are now stuck with lots of pixel perfect and consistent but otherwise broken and unusable apps.