I own Etymotic ER-4S and they are an excellent IEM. Their foamies provide exceptional noise reduction. In terms of isolation, it's the best I have heard rivalling custom earphones out there from Ultimate Ears, Westone, Sensaphonics.
It's nice to see Klispch finally jumping into the IEM market. I'm also very eager to hear how Custom 3 would compare to many top IEMs out there.
I Love iFi Sound signature a lot, it would be nice if Custom 3 has similar sound signature.
Portable1:iMod 80GB 5.5G -> ALO Cryo Dock -> Supermacro LE, Hornet M, TTVJ Millett-> Grado RS-1, Audio-technica W5000, Ultimate Ears Triple.Fi 880/1000(Ety foamies), Etymotic ER-4, UE-10 Pro, UE-11 Pro, Ultrasone Edition 9, HD650 Equinox LE, Westone ES2, Shure E500