It really comes down to what you really need. That often differs to what you want by a large degree. I had no real complaints with my PIII, even though it was fairly primitive by today's standards, I knew it inside out and could work really fast. Getting results is everything.
I tend to upgrade the computer in my studio every three years. The most recent upgrade was down to a Win 98/XP migration which my PIII couldn't realy handle.
My father however has to be seen to be believed with computers. He actually moves the mouse like a toy car and tries to 'turn courners' with it, when he wants to move the mouse left or right.
Bless him. 