Why does the font matter? This is a serious question. I use the default font on all of my editors and I've never had a problem. I can tell ohs from zeros and els from ones, etc. And I don't care about different types of serifs or other typographical nuances. Do most of the advantages come when using alphabets besides English?
A good font can make you more efficient. A font which is just as readable as another, but at a smaller size, gets more code on the screen. A font where you can more quickly distinguish 0 from O saves you some tiny sliver of time, yes, but more importantly, if the difference is great enough it can prevent distraction/context-switching.
Why are custom programming fonts so popular?