I used these everyday for almost a year, until I lost them. They're the best IEMs I've heard, but they are far from perfect. The most glaring issues are the fit, and the lack of bass. Once fitted properly, and using the right tips, isolation is incredible. I've almost been hit by cars multiple times walking around with these in. Again, once fitted properly, the bass is very high quality, but there just isn't enough of it to listen to hip-hop, or EDM. The mids are very uncolored an clear. The treble takes center stage, as it's as clear as I've heard on anything. It manages to do this without being painful. Imaging is almost as good as HD600s, and better depth, but as a result of them going so deep into your ears, the soundstage is very narrow. The cable is pretty noisy, but if you play music you won't notice it. Unfortunately, the foam tubes fit me best, but they fall apart every two weeks.

To wrap it up, these sound pretty great, but there are quite a lot of compromises. I liked/got used to these enough that I'm on the hunt for a used pair of ER4s.