> Think of how many windows you have open in the taskbar, and yet somehow you know exactly where to go to find the one you need.
That's not the same thing at all because 1) you have a visual indicator (app icon) to help you find what you need, and 2) you are likely switching between windows (thus reminding yourself of their position) much more often than switching between tabs on GitHub. What you're saying is true for power users, but anyone who doesn't use the UI very consistently will still need to scan the tabs to find what they're looking for, because there is no distinct, visual differentiation between them.
That said, I agree that it solves the usability issue you mentioned, I just don't know if this was the best way to do it.
