CM is really light. As an undergrad I had more trouble reading poor quality photocopies of notes in CM that my own notes not using CM did not suffer from.

In an extreme, one of my professors presented from notes and blew up his notes' display size like crazy, and I could never get a reasonably information-dense printout of those by printing multiple pages (those sizes were so large the fonts were too slim for the printer's resolution). Granted, it is an abuse of good typesetting, but I imagine my predicament would be helped with a font that had proper contrast.