I disagree. Essentially requiring tools for a supposedly human-readable markup nullifies the whole human-readable aspect. Tools such as equation editors can be a great boon, but those can be had without giving up being able to read and write the markup directly.
I do think it's a shame that browser support for MathML is limited or missing. I'd much rather have direct, native MathML support than nothing. MathJax is a pretty nice way to address this for now, I think. Much better than requiring random site visitors to install a plugin.
I was very impressed that it was able to interpret "min" with "x-2" underneath it, but if I wrote anything next to it the interpreter failed. I tried writing the "min" bit on one side and putting a very large parenthesis on the other side of the sheet, but it still didn't work.
Also, it handles \overline wonderfully -- impressively differentiating between an overline and fraction -- but it has trouble with the \underline. \Underbrace isn't working so well, either.
Yet another difficulty - "1 / 2" is turned into "y_2". The horizontal fraction delimiter doesn't seem to be recognized.
I've almost never seen an upright 'd' in mathematical literature, though it seems to be somewhat more common in engineering texts. Ditto for the imaginary unit 'i' and the constant 'e'. Matter of taste.