I was able to try out the iSine 10 and 20 yesterday in a store.
Unfortunately the seal of these things is a lot more finicky than I had anticipated. The store didn't have the earpieces on their demo pair, nor did they have different eartips since they're not your standard sized eartips. Lastly, the listening environment was bad - there was a store speaker playing some music about 10 feet away. Not too loud, but since these things aren't known to seal well, it affected things.
From what I could gather, the audio fidelity really is top notch. No distortion to speak of. No muddiness at all. No part of the frequency is overpowering. The iSine 20s have noticeably better bass and a fuller sound than the 10s. They can definitely rumble along. There was a bit of sparkle that I didn't appreciate though at 5500 Hz - not sure if that can be removed with an equalizer. The sound is definitely more airy and the soundstage is wider than an IEM, which isn't surprising. I had a few moments where the sound wrapped around me, but I wouldn't say that it's infinite as some other reviewers seem to think. Certainly no where close to, say, speakers. Or maybe I didn't have the right tracks. Not sure.
My S5 was able to drive them directly, but the volume was maybe at 80-85% to get a good listening level, so these would probably benefit from an amp.
My recommendation is that these are good for people who can guarantee they'll be using this predominantly in a quiet environment. Because they don't seal nearly as well as flush-fitting IEMs, I'm afraid that much of the audio fidelity and enjoyment would be lost in a noisy environment, such as walking around on the street, in the subway, etc. Plus they leak sound so they're not a good choice for libraries. But for the relatively cheaper price of $600, you've got $1000-level IEM sound quality.
If I were regularly switching between the analogue cable, and the lightning cable to accommodate different sources, this would be a nightmare. 
