I shifted my dev environment (Textpad :) ) over to using Microsoft’s new motospace font for Vista today - Consolas. First impressions: really seriously good. Previously I’d been using Lucida Console but Consolas is better in a whole load of ways: being designed for ClearType helps but what really gets me is the commas and semi-colons. Ampersands and zeros are also highly differentiated.
It comes with Vista and Office 2007, but the Powerpoint Viewer is free and has it if you don’t have the previous. Definitely worth a try.