Going OT here, but I've gotta defend the pixel font sizes. I used to do percents, (since I read somewhere that px is evil and zomfg never use it...) but I got tired of the constant "bug" reports coming in from the clients saying "it doesn't match the psd exactly on my Mac". Specifying them explicitly in px avoids this.
The way I see it, if you care about font sizes, go with px and match the design. If you don't care, just don't specify them at all. pt isn't reliable either; it is different across browsers, and apparently, it is only technically defined in print anyway. Moreover, the rest of the site's design is probably in pixels, so it is easier to see it fitting to stick to the same all along. Now, I hate all designer's choices (in my mind, graphic design is a synonym for incompetent producer of illegible ugliness), so in my main browser, I have a min and max size set, so I'm free of their bad decisions. Every browser in use, aside from the aging IE6, scales px fonts just fine too, so it is ok there.