I purchased RE0 after a lot of thought and research here in head-fi forums. At first I was puzzled by their sound. Having used only Sennheiser CX 300 before I found the sound to be too complex and the highs too pronounced. I had them playing virtually all day long (and night) for the first 3-4 days to burn them in as I knew that they require a long 150+ hours. I was also using them while burning them in to experience the differneces in the sound. The most notable difference was the bass, that really became more tight and clear. Bear in mind that I got used to such a sound signature about one, one and a half week after regular listening with them. Now the clarity is amazing, the highs are jaw-dropping, mids come clean and not overshadowed by bass and speed is up to par with fast paced songs. I tried listening to CX300 the other day, 1 month after I got the RE0. Couldn't get past 2 minutes, too much bloated bass it sounded like there was a cannon firing next to the band. I can't believe that I heard music before them. The few thing that bother me are the lack of bass body, since I am not using an amp (for now) and my source is a sansa clip+ and the fact that wearing them over the ear can be a bit bothersome and uncomfortable. Another issue it that they are very source revealing, so if you have low bitrate mp3 files, prepare for a big dissapointment as they will sound worse. All things considered, best purchase so far for me, and I am sure as time goes by I will just appreciate them more, and so will you.