Another user here with the ER2 (the SE).
I must say, even with all the hype, I'm impressed.
I've never heard any other piece of audio equipment (be it headphones/IEM's/speakers) that sounded so natural and effortless and, at the same time, so detailed. It's a revelation.
They have a very neutral bass response. In about 80% of my music, it sounds absolutely perfect. The other 20% would benefit from a slightly elevated response. However, at least for me, I believe the XR would ruin at least some of the other 80%.
Another surprise was the soundstage. I don't know if it's because they don't sound as "in your face" as I was expecting, but they actually sound quite large and airy.
For those that have them, they easily beat the Hifiman RE-400 and RE-600s, while having the same type of signature.
The fit is not perfect, but tolerable for me. I believe it will get better with time (on the second day with them, it was already better).
One concern for me is the cable. On first hearing, one of the sides was cuting. After pushing the MMCX cable onto the IEM, the problem solved. But I see this a common problem...