To point out another difference between audio and data on CD... With data CD's, there is extra error-correction. CD's only have a simple error-correction(With interleaving etc), because, for consumer-audio, it doesn't matter all that much. Since there is an analog part behind it that filters the high freq out of the signal, the errors that cannot be corrected by the errorcorrection will be less noticable because of the integrating behaviour of the filter!
The error correction that is foreseen for audio CD is on most players very bad implemented, because it simply isn't all that important. (The standard error correction is implemented, if the error is noticed by the system, but cannot be corrected, you can integrate the signal, regenerate the value some way, but since the analog circuitery allready does that partly...)
Anyway, the audio data on a cd has got standarized error-correction and interleaving. This is nowadays implemented in hardware, and is handled in realtime! (Actually, the encoding/decoding part of the CD/DVD chips is what I test at work...

) What you copy when you copy a cd, is the DECODED data! So first you decode the data, get most errors out by the errorcorrection, and then you decode it again and write it. So only VERY bad errors will result in noticable degradation, when there are to much of them. (I doubt that you will hear one wrong sample, taking into count that it's stereo and integrated by the filter...)
Not that I'm an expert on the field.
(By the way, the cd was developped for audio. A data CD is just a VERY BAD sounding audio CD. The standard is totally conform with the audio cd, but defines a higher level encoding in bigger blocks of data. Most audio CD players will mute the data because they know there's something strange about the cd.)