Just found a full review article for the Apple iPod in the latest issue of the Stereophile magazine. Here is the concluding remarks by John Atkinson, who did all the measurements:

The iPod's measured behavior is better than many CD players—ironic, considering that most of the time it will be used to play MP3 and AAC files, which will not immediately benefit from such good performance. But if you're willing to trade off maximum playing time against the ability to play uncompressed AIFF or WAV files, the iPod will do an excellent job of decoding them. Excellent, cost-effective audio engineering from an unexpected source.

Indeed, iPod review in an unexpected place!