> I just created a small experimental Emacs Lisp library that 
> emulates the tab bar feature provided by most modern web
> browsers, file managers and editors.  Tabs are very popular
> nowadays mostly due to their ability to group units
> equivalent to Emacs frames into one frame and providing
> handles to switch them quickly inside one frame without 
> having to switch top-level frames.

How does it compare with tabbar.el? I use that, and generally like it.

> Below is a screenshot how this feature currently looks in Emacs

Unsolicited feedback: Too much wasted horizontal space. 

See tabbar.el, for example: there is no horizontal space between the tabs (other
than their borders).

I customized the default tabbar.el faces, however - the default faces are
unreadable on Windows, IMO. Attached is a screenshot showing the faces I use, to
give you an idea of what I mean about the horizontal space.

HTH.