burn-proof is a wonderful thing... when i first got my 12x4x32 cdrw (w/burn-proof), i ran a torture-test of sorts that included burning an audio cd on the fly from mp3s stored on a couple of different machines on a network, while watching a dvd (software decoding on a k6-3/400) on the machine with the burner, encoding mp3s on the same machine, and streaming video (mpeg) between the two machines that the mp3s were coming from (both slower machines). the buffer was hitting 0% every few seconds, but the cd came out just fine.
btw: what i usually do (now) when making a cd copy is to check the box (adaptec cd-copier) to copy to the hard drive first and then burn. this way i can tell right away if there's a problem with the source material, instead of getting halfway through the burn and finding that the source cd has some errors.