It is a matter of preference, no doubt, but most developers I know prefer monospaced fonts. So what are the best ones to be used?
Over the years, I’ve tried numerous fonts and the few that work good are Monaco, Menlo, and finally Ubuntu Mono. Menlo is a great font that comes with OS X and is used in X-Code. It is also the best font so far that I found
I have recently tried to work with Sublime Text 2. I have used TextWrangler before but Sublime seems so much more powerful out of the box. I read somewhere that it is possible to setup TextWrangler with various plugins and extensions to make it quite powerful too, but Sublime Text comes already quite powerful out of the box and just feels more natural. TextWrangler never really felt natural to me but it was the best option I had so far as it had more options than Smultron.
So I tried Ubuntu Mono with Sublime Text but it looks almost the same as Menlo and since I am using Menlo with Eclipse already (Ubuntu Mono regular was horrible in Eclipse) I decided to keep using Menlo despite many praises towards Ubuntu Mono. But Ubuntu might be a good alternative for other OSes that do not have the Menlo bundled with it.
Happy coding!