I was waiting for Tree Style Tabs to switch to Chrome, finally gave up and switched anyway two weeks ago. While the vertical tabs option does exist in Chrome,

I was waiting for Tree Style Tabs to switch to Chrome, finally gave up and switched anyway two weeks ago. While the vertical tabs option does exist in Chrome, it's inferior to the Firefox offering in a number of ways. In particular, there's no tab grouping / collapsing, and the UI is really still ugly and not themable (at least on OSX, tabs retain their 'top tabs' shape, there's an unchangeable blue background on the tab bar, and tab dragging does not work properly). IMO, not ready for prime time yet ... hopefully soon though.