Maximum PC employs a few audio "experts" to see if compressed MP3 files make a big difference to sound quality.

With the possible exception of the USB Key that survived a washing and drying cycle, no other Maximum PC Challenge has ever surprised us as much as this one. It’s downright humiliating, in fact, that in many cases, we were unable to tell the difference between an uncompressed track and one encoded at 160Kb/s, the bit rate most of us considered the absolute minimum acceptable for even portable players.

They also come out pretty solidly in favour of variable bitrate encoding, which I'm sure is no big surprise to anyone.