Although it has taken me much longer than I expected here is the font hinting comparison I promised some weeks ago. The above image is a direct comparison between the four (auto) hinting options provided by FreeType.
The most striking thing is how poor the "Slight" and "Full" hinting options look. (Although they look similar closer inspection reveals them to have some subtle differences.) "None" and "Medium" both produce acceptable results, however. The most notable difference between the two is in the infinity symbol: notice how it is much more consistent with "Medium" hinting as opposed to "None."
So why does all of this matter? Well, rendering quality is extremely important, especially when bitmapped images are being produced -- a potentially common use case for the resulting Mathtex library. Therefore it is important to know exactly how the various rendering options affect the output in order to choose sensible defaults.
About the samples: these were all produced using the svn HEAD version of matplotlib using the Cairo backend (which when running under Linux uses FreeType + fontconfig, making it easy to change the hinting method).