If you're on OS X and like Vera, you might take a look a Panic Sans, included in the app bundle of Coda. It's a tweaked version Vera Sans Mono. I can't put my finger on what they tweaked, but it's been my preference for some time now.
I second that. Liberation Mono rocks. And it is updated somewhat frequently, so it might be worth checking for a newer version or to install on a Mac. (they put a dot in the middle of zeros a while back, for instance)
Yes. I guess it was Bjarne who convinced me to try it (The C++ Programming Language book was set with a variable width font).
I find it pleasing to the eye and the sacrifice is .. well, what? Indenting still works and I don't do the block-style formatted comments etc.
Agree with these criteria. I personally like also some "airiness" so the Bitsteam Vera Sans Mono mentioned seems a bit too compact for me, but the Liberation fonts were a nice surprise.
Personal favorites include Andale Mono, Dina and Consolas (Inconsolata is sometimes adequate except it doesn't seem to scale well to different sizes). For some reason I've always used Crisp for javascript, even if it too does not scale well at all, and is in fact too small for my tired eyes.
http://img376.imageshack.us/img376/1897/picture68gr5.png
It just looks fantastic to me — I simply don't get the attraction to fonts which look like they came directly from a 1970's typewriter! :)
(good anti-aliasing on OSX helps too...)