I use the stuff all the time... Not for final sanding of course as NW mentioned, BUT, it works great when doing the initial prep on door, hood and trunk jambs. Use the fine or extra fine pads and have some hot water mixed with TSP handy. I will never use sand paper in the jambs again because the pads do a much better job at getting into the corners and conforming to surfaces.
I will also use them between primer surfacer coats if there is no blocking to be done... Don't go overboard with the pressure, use them with a backer and they do as good a job as dry sanding with paper. They do a good job of knocking down local dust nibs also without having to sand an entire panel to get the surface consistant.
Mark