I upgraded from the Pre to the Nexus S 4G saturday. After reading that the nexus had a high end audio converter built in (wolfson), i was sold. Before installing the netarchy kernel, i listened to some tunes on my Vmoda earbuds. The quality improved dramatically with the netarchy kernel and voodoo control. There is much more detail in music when listening thru headphones. This is the best mobile listening experience I've ever had.
As i type, i am listening to the "this is my next podcast" on my plantronics backbeats using the site's flash player. Even the bluetooth playback is far superior to what i experienced on the Pre. With the Pre, bluetooth music sounded over compressed and signal was too weak to use the backbeats while walking with the Pre in my pocket. With the Nexus, everything is greatly improved. Music, while not as pristine as corded playback, is satisfactory and i hear no apparent compression artifacts.
Music and podcast listening are very important to me, and I'm stoked about my decision to buy the Nexus. I highly recommend the Backbeats and Vmoda headphones. If music is important to you, quality headphones are worth the extra money.