I was pretty sure this was the case, but now there is a recent double blind study that shows that people can’t hear the difference between the sound from CDs and the higher resolution SACDs or DVD-A.

Also, it is difficult to hear the difference between MP3s with high bitrates and uncompressed audio straight from CDs. If you want to retain the audio fidelity of your music, but you want it in smaller file sizes, check out Hydrogen Audio for a lot of information on compressed (and uncompressed) audio formats.