🚀 go-pugleaf

>I also claim that an OS that is not multitasking does not automatically gain
> any significant advantage _by_not_being_multitasking.

In that I think you are seriously wrong. It gains freedom by not having the
OVERHEAD of a multitasking monitor. One does not have to worry about 
interfearing with another task. There is no need for code to PREVENT
interfearance. Just compare the ease of writing full-function programs
(defined as one that makes full use of the machine, using all its resources,
including the screen) for MS-DOS compared to Unix (as a particularly
strong example). I STILL have not heard of ANY full-function program
running on an IBM-PC using a UNIX variant (in this case, by full-function
I mean using all the bells and whistles of an EGA or VGA screen. Most
arcade-style games are examples of full-function programs.) 
The defination of all the "windowing" systems I have seen prevent using
full functionality. (Even on high-end graphics workstations, e.g. a
top-of-the-line Silicon Graphics, different windows interfere with one
another at the color map level.)