I have Vista on my wife's computer. It is prettier than Windows XP, but it is absolutely HORRIBLE. Very little software designed for XP works right. They went to a completely different help file standard so none of the help files in older software are worth anything. It crashes if you sneeze. It crashes if you breath. It constantly asks you whether you intended to do what you did. I just outright hate Vista.

Now with that, I've used Madrake and RedHat linux. They hardly ever crash, but you need to be a computer scientist to do much. Not very plug-and-play user friendly.

Out of all of the OSes I've used, Mac OS X was the best in terms of usability with respect to the non-coder end-user, and stability.