Description
It would be great to have a description of the exact subset of LaTeX that is rendered by the default version of matplotlib (with usetex=False).
And it would also be useful to have an explicit statement about some commonly used packages that are NOT supported. In particular, many of the queries about LaTeX in matplotlib, both here and on stackexchange, reflect users' (incorrect) expectation that the American Mathematical Society packages are built in. Many scientific papers begin with
\usepackage{amsmath, amsthm, amssymb, amsfonts}
so that writers are not aware that tools that they use all the time are not actually part of the base distribution of LaTeX. (It would be great if a future release of matplotlib could include the functionality in these packages -- but I realize that is harder than it sounds because matplotlib's fast and compact built-in renderer is hand crafted).