I've kicked around Sys (http://www.fsd.it/fonts/sys.htm) for this purpose before and like it. I'd rather code in a proportional font, but I feel like we need an editor designed for one, which we really don't have right now. Univers is also all kinds of beautiful.

I've tried out a bunch, and I haven't found one I like better. That said, Open Sans looks pretty good, and you may like the sans sarif style better. If you find anything awesome, I'd love to hear about it!

I've been using Georgia for years and really like it. Much better than Times New Roman, both for coding and for general reading.

Georgia is a pretty hardcore proportional font, though. Even the numbers are proportional, where most proportional fonts have monspaced numbers.

Giving it a shot. I think I tried it out when I first switched, and wrote it off for some reason or other... but it's probably worth re-visiting. :)