Nicely formatted math does look nice.
However, do we really need it?
Stackoverflow.com doesn't have it because ("it is an extremely heavy dependency."). I presume Jeff meant in terms of page load/page render (the math renders a second or two after the initial page load).
Anyway, the majority of questions and answers are about games and game development, not "neato math tricks."
Joe's comment here says it better than I have here, I'll repeat it:
I'm not against it, but I also feel like if a question requires that much math in its answer, it's probably more suited for math.se, not here. Math here needs to be translated into readable code eventually anyway, so I'd encourage code-like answers rather than math answers.
Outside of the occassional exponent or subscript (for which we can use HTML), do we really need 1st class presentation of other mathematical constructs? I would vote that we don't need them at the moment.