I have used the 5 pros, and the E4Cs, and the ER-4Ss, and I have to say that the ER-4S is grossly superior to all of them. It is by far the most
natural sounding headphone I have ever used. They weren't kidding when they said "MicroPro earphones are designed to match the acoustic response of the open ear."
I have found them very good for all types of music listening, even rock and hip hop. They will present the music to you exactly as it is, without any coloration of their own. They are capable of resolving a large amount of detail. They are not overly analytical unless you make them that way. I have no problem being absorbed into the music while listening to them. When I listened to the song "Barcarolle" from the "ARIA: The Animation" soundtrack, I could have sworn Kawai Eri was standing right there, singing just for me. Wonderful.
To me they are not harsh. Not even a little, bitty bit. The treble sounds completely natural. Almost all other headphones I've tried sound dark in comparison. Perhaps this is why so many people dislike them; they're so used to slow, dark headphones, that anything with a normal amount of treble sounds harsh. The bass is neutral, deep, and very tight. Sometimes I can even feel it shaking my ear canal.
My Grado SR-60s sound positively boomy now, after listening to my Etys for a while.
All in all, the best headphone I've ever heard.