I'll echo the others who have endorsed Emacs. I program every day on, at a bare minimum, OS X, Windows, and Linux. Having the same IDE on all three systems gives me an enormous productivity boost. That said, the vanilla version of GNU Emacs...well, it sucks. I'd strongly encourage you to try EmacsW32 instead. In much the way that Aquamacs makes an OS X-friendly version of Emacs, the EmacsW32 project makes Emacs out-of-the-box work just like a Windows text editor. Mind you, all of Emacs' power (and complexity) is there, but if you don't already have muscle memory built up, there's no reason not to use Ctrl-C/X/V as copy/cut/paste instead of M-w/C-k/C-y just to be cool. EmacsW32 also brings Windows-compliant open/save dialogs, sane CRLF file handling, and quite a bit more. If you've ever had an itch to try Emacs, give it a shot. You won't regret it.