PostScript outlines for smoother rendering on Windows
Mandy Brown, writing for Typekit:
Due to a quirk in the GDI rendering engine, PostScript outlines cannot be rendered with ClearType, but rather display using grayscale antialiasing. Grayscale antialiasing smooths in both directions, and looks great at large sizes. So we can improve this rendering scenario by serving PostScript outlines instead of TrueType.