Mozilla Connect

Great news!!! @asafko , the first link ("thread to follow the updates") does not seem to work. Page not found.

For me a nice to have. I personaly find tab grouping confusing and do not use it. (However from previous comments I see other people do). 

There are extensions like Tree Style Tabs, but then you have to mess with chrome.css to remove the no longer needed horizontal tab bar. This is clunky. Vertical tabs should be implemented natively. There should be a switch in the settings.