Works for my nackered games and i haven't had any problems with them. It'll only replace the code that is scratched on the disc, so if u could tolerate playing the crapped up original i doubt u'll care if the back up plays the same.
But obviously u r gonna get better results if u r copying a decent disk in the first place.
But if u r like me and r happy with just playing the game to a sub-perfect standard then just set the error recovery to replace

nobodys perfect
4nim4l.