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.