Tabbed browsing is the area where most GUI-related addons could fall into.
Tree style tabs, tab previews, Colorful tabs, Tab mix plus…
Each introduces author’s unique coding style, their concepts and purpose overlap, introducing leaks and bugs when used several together more often than not.
Opera already offers vertical tab bar with page previews.
In Firefox, you’re left with 20 tabs to see at most to read at least a few letters of the tab title, even with a really large resolution display.
Besides proper session management it’s the basic old thing that must be addressed in FF4.0, finally!
That and a few UI hacks (autohide menubar+toolbar, drag-to-scroll, resizable textarea) are absolutely necessary, rather than arguing about yet another default theme modification or renaming menu items.
