[whughes]

Tree-style tabs:

https://addons.mozilla.org/en-US/firefox/addon/5890

Still not matched anywhere else. The bogging-down from ridiculous numbers of Firefox tabs may soon force me to switch, however.

I also like some of the highlight plugins for translation and search.

[endtime]

Ah, the tabs tree does look useful.

Opera 10.50 has new search highlighting, though, and the right-click context menu for highlighted text has included a translate option for a while now.

[fnid2]

Tree style tabs would be better if the tab panel would expand and put thumbnails under the links. I don't like that they automatically collapse either.