My three favourite fifties are all 50/2 and one of them is a macro (Zeiss): indeed, it qualifies as an excellent allrounder. I never felt frustrated by not having wider apertures, even though I occasionally enjoy them. For handheld night shots, f/2.8-f/4 is my normal range (in conjunction with the Df and ISO up to 12800). f/2 provides some little extras, such as a slightly brighter viewfinder, shallower DoF of course, even smoother bokeh, and some built-in vignetting, so I already feel spoiled, but that's more for daytime shots. For macro alone, f/2 is of little interest.
I use f/2 less often on the Nikkor AI because optical quality is not stellar (fringing) and still do not feel frustrated.
The Leitz Summicron R is very good and consistent at f/2, somewhere between the other two, and I use that aperture very often. Same with my second-most loved one (50/1.2 AI).
Bottom line, I share Roland's view - a 50/2.8 macro is ok, but wider would really be appreciated to make it an allrounder. I do not care about AF, and even the focussing mechanism is not very important to me because I prefer to move the camera or, when possible, the subject, after having set the magnification ratio.
I'd be surprized to see yet another 50 AF macro, after Nikon has released its "Noct" 50/0.95 with manual focus... that would really reveal a compromise for allround usage, in which case the max aperture should also be wider than 2.8. Otherwise why care - just get a 50/3.5 macro.