I know that I have been harping on Operating System issues lately but due to working requirements of VPN clients, special development licenses for 3rd party tools, etc., I have been spreading my time fairly evenly between Ubuntu (Gnome desktop), Mac OS X, and Windows XP. For my work flow, Linux is just simply better except for:

• Windows: TortoiseSVN (love it!)
• OS X: OmniGraffle drawing program (love it even more!!) and the TexShop Latex wrapper

While OS X is very nice, I simply find myself not using stuff like SpotLight, etc. very often. I am probably a bit biased (using X Windows since 1988) towards Linux and Gnome (I also find KDE to be very good). The good thing (for me!) is that I hope that most people do keep using Windows: a honey pot for virus writers and I get a professional advantage over developers who code on Windows:-)