Quite frankly Xp like most of Windoze OS's was a bit of a dog at first but over time it's developed and IMHO, one hell of a good OS these days. Sure you get the odd useless errors but everything is easy to work on and is so frugal with it's hardware.
Vista was utter s***e to put it bluntly, but thankfully has been replaced with 7 which I hear isn't a bad OS, though is still power hungry.
NT was another good bit of work from Bill if you ask me.