Here is the current traffic data for buymusic.com from Alexa.
I started wondering about this after having tested it on a friend's Windows XP box. The experience was detailed on this page and was - in a word - substandard. In talking with others I have only heard from two (out of many Windows users questioned) who had tried the site. The Alexa numbers (assuming they are in the ballpark) show that buymusic needs to rethink what they are doing.