These days I spend most of my time working on machines running XP that have more than one monitor hooked upto them. XP's support for multiple monitors is pretty good apart from one little niggle. You only get a toolbar on the primary window. To get around this I use a piece of software called Ultramon. It adds a toolbar per window and little buttons to the tops of windows that allow you to switch them across to other screens easily. There are more functions in Ultramon that I don't use like screen saver and wallpaper functions but I don't need them.
I installed Vista on my main machine at home a couple of months ago, installing XP, Vista and Ubuntu, each on their own disk. Originally Vista was the RC2 release, a late beta that wasn't 100% stable, so last week I installed the Business edition that I've had kicking around for a couple of weeks. So far I've been fairly happy with it, not booting back into XP once since the install.
I'm a big fan of the Windows SSH client PuTTY. It's a small, single executable that doesn't need admin rights (I've used it in EasyNet cyber cafes before now where the security is pretty rigid) that simply works. The SSH tunnelling works well and gives me a lot more flexibility in 'corporate' environments.
After fiddling around with Linux I decided to keep things simple and went for a complete XP based build. I've got a spare hard drive in the box and I'm planning to put a Linux partition on there so that I can play around without destroying my work environment.
I've discovered that Linux is improving, but, at the moment, Windows is still a nose ahead when it comes to putting together a complex web of hardware and software requirements for desktop use.
I started having problems with my desktop PC last week. It was getting slow, sometimes hanging or rebooting itself with no apparant pattern. I tried a rebuild with both Windows XP and Ubuntu Linux and had problems with both. The CPU would go to 100% for no particular reason.