I'm using Macs a lot at my new company, and one thing that really bugs me is the relatively poor quality of anti-aliased fonts on OSX, compared to recent versions of Windows. I found this to be especially true for fixed-width fonts used in programming IDEs. The default fixed-width font, Monaco is just a blurry mess at small point sizes, especially for characters like "=".

A bit of web searching brought me this excellent web page that describes a variety of alternative fixed-width fonts available for the Mac, with some handy screen shots to make it easier to choose one:

http://www.cfcl.com/vlb/h/fontmono.html

After viewing that page I was almost tempted to use one of the gaudy Celtic or pseudo-handwriting fonts listed there, but in the end I chose the Osaka regular-mono font, because it looks good and it's actually installed by default on Macs, as part of the Japanese language support.

Osaka seems to rasterize much more cleanly than Monaco at equivalent point sizes. Osaka does have the down-side of being very tightly packed vertically, so you might want to add some extra space vertically if your program lets you do that.

(I like using Anadale Mono on Vista, but it just doesn't look as good on the Mac as it does on Vista. This would seem to indicate that Microsoft's font renderer is better than Apple's, at least at small font sizes. Good for them!)