As highlighted recently by Jeffrey Zeldman, Firefox text rendering lags behind that of Safari, or rather Gecko lags behind WebKit. This is because at present, Gecko browsers use the older Quickdraw graphics library, originally developed for OS 9, rather than Quartz, or the more recent Core Image libraries. Its been the main reason I prefer Omniweb or Safari over Camino/Firefox, text just looks SO much crisper and smoother.
Things are about to change however, as the switch to the Cairo graphics library in Gecko browsers will allow them to use Core Image on the OS X platform. There is already a developer release of Firefox 3.0, codenamed Gran Paradiso with Cairo enabled. You can also grab a latest trunk build of Camino, which also uses Cairo.
The improvements are already easy to see. My personal rendering bugbear has been the sub navigation on Amazon, which always renders roughly, particularly in Gecko. Compare these screenshots:
Not only is Gecko with Cairo improved, it actually looks better than WebKit!. Looking at the example that Zeldman used, italics are MUCH improved also:
It’s early days so there will be plenty of bugs, especially as the Mac platform is behind Windows and Linux, who’ve had Cairo enabled for about 6 months now. Testers are needed for OS X, so if you can lend hand, so please do grab a build and get reporting those bugs.