I am worried by this trend towards using a custom typeface to store icons. Firstly, whilst it looks great in the giant preview pages linked to on HN, these icons often look terrible at smaller sizes / without anti-aliasing. Secondly, whilst they're undoubtedly efficient when you're going to use a lot of them in various sizes, I question whether that's still true compared to an optimised PNG sprite (which coincidentally can solve the first problem too).