I took part in some Emusic customer satisfaction survery, and when I complained about the mp3 quality they told me they were aware of the problems and had already ripped all of their collection to wav to prepare for a re-encode. This was a few months ago.

Some tracks seem worse off than others. With some of the bad tracks you can :

* Use lame or some other encoder to re-encode the mp3. I found that if I use lame and encode back to mono I ended up with a better sounding clip. (Yech..)

* Use napster and find a better version of the track you payed for..