In my experience, proportional typefaces only work for code if the IDE/editor is using a pretty-printer that uses word-processor style indentation.  (That is, it uses tab stops as opposed to just inserting spaces/tabs in the text.)<p>The only IDEs I've seen work this way was the old THINK Pascal from the 68k Mac era, and its predecessor Instant Pascal for the Apple II.  Anybody else seen a more recent example in the wild?