If the data is important to you, then your backup is not complete, on a failed verification process.
If they are just some mp3's and files you can live without then OK but you have to decide whats acceptable for you to lose.
Failed to read sector xxxx will result in 1 maybe 2, 3, 4, X amount of files who knows how many files may not be readable.
If its important then use good quality write once.