I have a 1ds mk1 so i guess that answers the question
if you need fast iso quality, saturated sharp images straight out of the camera, with easy to use controls and large rear screen and good battery life then 5d
i like to think of the 5d as a small car with the big engine - ford escort cosworth
if you want built like a tank build, with endless customisations and control set, together with a professional "built to get the job done" look and feel, older technology but at the time best you could buy - 1ds mk1
I like to think of it as an old quality car - Daimler, Jaguar etc