dvd shrink is a transcoder, most of the one click copiers are transcoders - they are horrid.
a transcoder acts like a comb, it sweeps across the video frame by frame and removes half of the data, resulting in pixelation during fast movement scenes.
the only real way to ensure a quality (yes quality) backup is to re-encode the mpeg2 video... easiest way is to use dvd-rb (dvd rebuilder) on pc, not sure on a mac, but re-encoding the video results in a FAR superior picture quality than using a transcoder, of course it can take between 2 and 8 hours per movie depending on your CPU.... but then again who cares, you bought that big powerful cpu to do something, right?
takes 3 to 4 hours on my P4 3.0ghz per movie, time well spent IMO... I just do other stuff while it goes, over before I know it.
probably not real efficient if you are renting 3 movies a day from blockbuster and returning them the same day though - but you guys wouldn't be doing that.