I notice a difference at about 90% - 92%. It depends if you will be watching the movie on your comp or TV. I usually use the deep analysis option for compression of 90% or less.
As the man said, it's in the eye of the beholder.
If you have a LCD or Plasma TV you're apt to see differences sooner than later. If you're an average TV watcher, just sitting 6 to 8 feet from the screen watching the show, you can go some before it looks a VHS tape more than a DVD.
Now that the new, improved DVD Shrink has a Deep Anaylsis AND a Quality Enhancement feature, I recommend that you use them as soon as they come on (which is when any compression at all is required). By using those features, compression to 60% still comes out pretty well (Im now a convert using Maximum Smoothness all the time) after processing the DVD.
As I said when I began, everyone has their own opinion, try it yourself, since it's FREE, there's no earthly reason not too.
