I think I once had a CD with some scratches and I ran it through twice but got the same checksum...can't see me bothering with many, really, unless I get a few CD's with issues. It only takes about 15 minutes to rip and encode an entire CD on my box anyway - takes me a reasonable proportion of that time to type in the track info, as it's on a machine I don't connect to the World Wide Interweb Superhighway.