I could not say it better about XP . I'm using it, tweaked - also in the GUI ! - secured and strengthened with third part softwares. I don't need any else Windows OS.
I ran every single one of those. I voted Windows 2000 because it was the one that felt like the best investment at the time. It was way more stable than Windows 98 and more compatible than NT 4.0. I couldn't wait to get off of 9x and 2000 was the version that allowed me to do so.
I've got the feeling that many businesses still use XP. At least it will be supported through security updates until April 2014. You're lucky blacknight.