Safari’s font rendering is a bit different from Firefox’s. For example, when you use the CSS3 property text-shadow on text, the more you blur the shadow, the lighter the text becomes, whereas in Firefox, font weight is not affected by text-shadow. Some designers use this feature/bug of Safari to create some interesting text varieties, such as zurb.com. Safari 4 also has its fair share of text-rendering bugs as well, one of which is illustrated in this blog entry by Rogie King. There are also minute differences in normal text-rendering, but the difference is almost imperceptible.
Now if only Firefox would implement the sweet transitions that Safari 4 has, then I could completely ditch my bulky scripts to make smoothly fading links.
Apparently, the forum also supports Textile formatting. Sweet.