I've copied about 60 or more of my DVD movies and only one DVD couldn't be copied and one copy would only play on my computer. The others work great. BUT:

1-I only copy DVDs I purchase NEW at retail stores or online (usually deepdiscountDVD.com or Sam's Club). I still own and possess all of the original DVDs I have copied.
2-I've never tried to copy a rental (and I never purchase used DVD's that might have been rentals) so I don't know if they would work.
3-All 58 or so successful copies made with Fast DVD Copy will play on both of my Sony stand alone DVD players without a problem (different models). NONE of them will play on my Toshiba (older) stand alone or Philips combo (1yr old). All four players have no problem reading the media I use (BeAll) when it's the home movies that I make on iMovie and iDVD. Fortunately, the two Sony players are the ones I use 90% of the time so I'm a happy camper. They will also play on a friend's JVC stand alone player.
4-I do not work for the MPAA or any company that is a member of the MPAA. ;-)

This software is simple to use and produces great copies relatively fast on my 20" iMac G5 with SuperDrive. They just have to be played on players that can read them.