Typically I either work in a terminal emulator or in a GUI based editor and the amount of time I spend looking at either one of these is simply scary. So is there any font that makes work like that easier on the eyes?
I code in 9-point Menlo (antialiased, of course) on a pair of 30" 2560x1600 displays, and it is awesome. Before that I used Consolas. Before that I used Bitstream Vera Sans Mono and often googled for programmer fonts. But none of those could ever go for hours at 9-point size without bugging me. (I prefer Menlo at larger sizes, too.)
One interesting thing is that the font looks noticeably better on my Apple 30" Cinema Display (from 2007) than it does on my Dell 3008WFP (from 2008), both hooked up to the same Mac Pro. Not sure if that's just a coincidence or whether Apple really did some kind of freaky font-tuning for Apple gear. But anyway, coding font has been a kind of personal holy grail for me for years and years, and Menlo is my #1 favorite thing they added in Snow Leopard.
I've been using Inconsolata recently and so far so good.
Some more discussion here: http://hivelogic.com/articles/top-10-programming-fonts
And then there's this: http://www.lowing.org/fonts/