Many of my papers are written in TeX. These typically use Computer Modern fonts. I want the diagrams to fit well with the running text, so I should use the same font for both. Few fonts other than CM have the right sort of math symbols. The math in these papers must be in CM, so the running text should be in CM, so the diagrams must be in CM. For diagrams created with MetaPost, that’s no problem. About half of my diagrams are created with OmniGraffle.