Most people who have owned IDI's will say the same thing....slow, but they miss them and want another. They arent fast, but they definatly get the job done. A simple motor, easy to diagnose problems, easy to fix, and most parts are cheap (you can buy 8 new injectors for the price of 1 new PSD injector).
The first gen cummins are the same for the people who owned them. They tend to be more expensive, and you cant get on with a crew cab like you can with a Ford.