Yeah, I use it as my main OS. I'm more used to it than I am to Windows. The user interface is much more customizable, and installing software is much more convenient. Plus it doesn't cost anything. With Windows, the price of the OS is usually built into the price of the computer, but you'd still have to pay when you upgrade to a new Windows version. On most Linux distros, you don't have to worry about that kind of thing.
The only reason I never use Ubuntu is the difficult setup for modems. No matter what I seem to do, I haven't had any luck. I even joined a support site, but to no avail.
Oh well. I like XP.
PS
Luna is way to happy and eager to know she has a fan.