At first glance I wasn't sure about removing the left hand menu, but then I realised how everything opens up as a tab anyway, your suggestion makes sense. It's useful to have as much usable space on screen as possible, so reducing unnecessary clutter is helpful.
I like the idea of distinguishing between different kinds of tabs through colours or icons. It's confusing when you end up with a mix of static/pinned tabs like Branch Explorer, Workspace Explorer, buried between more ephemeral tabs like merge results, 2d history views, where it's easy to forgot why they were opened in the first place.