How well hinted are the common icon fonts, actually? Given that many (if not most) freely-available typefaces are actually not hinted at all I'd be a bit skeptical. Autohinting doesn't really produce very convincing results for typefaces, I wouldn't expect it to do wonders with images either.
That's a good question. I know that the Font Awesome project has better hinting for smaller sizes as a stated goal. Currently hinting does seem to improve their icons at 12pt but below that, it doesn't give much help.
Subpixel rendering is, of course, very helpful. It's really preposterous though that we have to resort to abusing fonts to get subpixel when implementing it for arbitrary vector rendering is so straightforward.
The other big problem with using fonts for hinting support is that people have differing opinions on the value of hinting for fonts, but everyone would probably agree on the value of hinting for icons. If you disable hinting because it hurts your eyes (or because you use OS X and don't have a choice), then you're going to miss out on icon hinting as well.
Seems to me what we really need is a client side solution for rendering arbitrary SVG with either manual hinting or icon-optimized autohinting (which might be too general of a concept to be doable).
