A few users reported on issues with anti-aliasing of webfonts. Almost always these issues were local, and impossible to reproduce on other computers. While we don't know exactly the source of the problem, the problem seems to be caused by the OS, and not the fonts.
Using external monitors on MacOS is a possible problem, there is a bug in Snow Leopard that disables LCD font smoothing, and there is a Terminal command that fixes it. http://hints.macworld.com/article.php?story=20090828224632809
This is a known Webkit bug — any text with @font-face applied will be rendered without anti-aliasing if there is a text element without anti-aliasing applied preceding it. The bug is described here: http://konstruktors.com/blog/web-design/3190-webkit-bug-anti-aliasing-for-font-face-fonts/
If you experience a similar problem, please report the specific applications and OS that you use.