Impressive step forward with electrostatic technology. It provides an astonishing quality of the sound. Music cannot be more real and natural than this, even comparing with more expensive flagship items. I prefer KSE1200 over the KSE1500 because I do not need the built-in DAQ. Not worth in my opinion using a separate good quality DAQ.
I've read other reviews claiming the sound is flat, true,
but flatness is not a common feature of iems, even flagship iems. To be neutral and transparent doesn't mean "boring", not at all in my opinion! Basses are there but you don't hear the "humph"....who said that? I think that if you don't hear basses, the sealing is not perfect. In this respect I have only one suggestion (and a small critics to Shure). Included eartips could be of better quality. I immediately substituted the original ones with silicone SpinFit eartips CP-800. The seal was perfect and the sound quite different. Basses are definitely there, with an unprecedented and unheard quality.
In conclusion, I agree with siruspan: once heard you will never forget the perfection of this sound.