There are several more specifically active folks in this topic who will, I imagine, show up later on; I'll wade in just to get the ball rolling...(hey guys, where are you?)
Whether there's a stigma or not about an Art Ed degree, to my mind, wouldn't be the most important issue for someone with a strong portfolio; if that's what they want, that's what they go for, and do their own painting/sculpting/installation/other work for showing as they wish/are able. The things I would have in mind are:
a) The MFA is a terminal studio degree, which is seen as adequate for getting studio teaching work in the university setting; as far as I know an Art Ed MA would be for teaching art in elementary school or high school.
b) Others may know better, but an Art Ed Ph.D. sounds off, to me. I'm not sure but what you'd end up getting an Ed.D. instead, which probably would not weigh in at the same level as a Ph.D. for university work.
c) Can't speak to this...in general, everything depends on where you come from and where you go, but as to the nomenclature and interpretation of the degrees, I believe there is some standardized terminology; try the CAA (College Art Ass'n) website:
http://www.collegeart.org/guidelines/Again, several others may have better and more specific ideas about this.