I think CDRs sound fine for listening to MP3 sources or in the car. On my home system they are clearly marginal. Why? I think the primary reason is jitter. The CD burners clearly don't have the jitter specification that the original stamping process had. Stereophile ran tests about 5 years ago during a controversy that centered around whether different CD plants produced better/worse CDs from the same master source. BMC was the target of those complaints. The bottom line was that the various copies were absolutely identical bit for bit but they sounded different. That was the time when the significance of jitter was just becoming apparent. So it the pits are shifted ever so slightly because of a not absolutely accurate spin speed a phase shift or random jitter can be introduced.
