I have to archive a large amount of data off of CDs and DVDs, and I thought it was an interesting problem that people might have useful input on. Here's the setup:

The script will be running on multiple boxes on multiple platforms, so I thought python would be the best language to use. If the logic creates a bottleneck, any other language works.
We need to archive ~1000 CDs and ~500 DVDs, so speed is a critical issue
The data is very valuable, so verification would be useful
The discs are pretty old, so a lot of them will be hard or impossible to read

Right now, I was planning on using shutil.copytree to dump the files into a directory, and compare file trees and sizes. Maybe throw in a quick hash, although that will probably slow things down too much.
So my specific questions are:

What is the fastest way to copy files off a slow medium like CD/DVDs? (or does the method even matter)
Any suggestions of how to deal with potentially failing discs? How do you detect discs that have issues?
Writing your own backup system is not fun. Have you considered looking at ready-to-use backup solutions? There are plenty, many free ones...
If you are still bound to write your own... Answering your specific questions:

With CD/DVD you first typically have to master the image (using a tool like mkisofs), then write image to the medium. There are tools that wrap both operations for you (genisofs I believe) but this is typically the process.
To verify the backup quality, you'll have to read back all written files (by mounting a newly written CD) and compare their checksums against those of the original files. In order to do incremental backups, you'll have to keep archives of checksums for each file you save (with backup date etc).
What is the best way to archive a data CD/DVD in python?