I’ve tried Fira Code before, and I think it goes a bit too far honestly. It’s nice that it preserves character widths, but ideally I’d like to get away from monospaced fonts as well—they’re pretty much just a holdover from the technical limitations of typewriters and text displays. The main reason I don’t use proportional-width typefaces in programming is that I like to work in a text-only terminal (to avoid distraction) and that the ASCII-art approximations of symbols tend not to look very good.
