Are there any other mathematicians out there? I love TeX, while freely acknowledging that it has flaws, but maybe it's just because it is the water in which mathematical writers swim, so that we learn it from such an early age and it becomes essentially inconceivable to use anything else.
The author carefully notes that the blog is not typeset in TeX, but I was disappointed that someone who cares for typography would think that the point of math mode is to shove everything in an <em> (not even <i>) tag. TeX sets what it thinks of as variables in an appropriate slanted (not exactly italic) type, but it would not (unless specifically instructed to do so) put the exponent 2 in y = x^2 in that same slanted type.
(Incidentally, the Turing completeness that the author mentions was against Knuth's original vision for the language; as the mythology around TeX goes—although I can't find a source right now—he added the relevant extra power (I'm not sure what it was) only "reluctantly." At Guy Steele's request, by the way!)