Got mine in today, been listening to them for about 1.5 hours now.
First impressions: These are VERY good.
I was worried about them sounding "only" like IEMs based on the review I read at Metal-Fi, but while I can see the spirit of what was meant by that comment, I disagree.
These, like many have already said, sound WAY bigger than they are. You CAN'T judge these as IEMs.
The first thing I did once I finally got them settled in my ears was play some music on shuffle from my DAP. The song that played happened to be "You've Seen The Butcher" by Deftones.
Coming straight from the headphone out, unamped, the sound as the music started playing was so FULL. I don't think I'd ever mistake these for over-ear cans in terms of sound, but it's like @Kazekeil said on Reddit when talking about the i20s: they sound like the essence of over-ear cans piped directly into your ears (paraphrasing). The guitars dropping in out of nowhere on that song sounded huge and full (I'm going to keep using that word).
I let my GF try them and her eyes widened as I started the song over for her. She was just as shocked as I was at how good they sounded. She mentioned that the bass was a little lacking in her opinion (she's so observant for not being in this arena), which I agreed with, but I guessed that some amping would do them some good.
Plugging them up to my Fiio A3, throwing on some Gojira, my suspicions were proven correct; drums hit quite hard and are FAST (yay planars). Not the slam of a "full-fledged" can but very respectable. And should I want more, the A3 has a nice subtle bass boost that provides even more low end when needed. Vocals are forward, but not too forward, just more forward than some earphones.
But the last straw was plugging them into my O2+ODAC. Navigating to Glass Animals 'Flip', which has recently become one of my go-to songs for bass-testing, the deal was sealed. The bass filled my ears almost as full as my HE400is and just as clean. I say "almost", but really, it's hard to compare the two because the i10s present the music in such a different way.
Leak testing: compared to my HE400is, which are very open and leaky, and which my GF rated a 7/10, she rated the i10s as a 2/10 when I was sitting right next to her listening at lower volume, and a 4-5/10 as I really got up there in volume. And sitting at my desk 4-5 feet away with my music turned up to a respectable level (about my normal listening level with my 400is), she said she couldn't hear a thing (this was with no AC running, nothing else playing in the room, just ambient outside noise).
Isolation is pretty much totally non-existent. I had a full conversation with my GF wearing them with no issues. When the music is turned up, there is more passive "isolation", but I can still hear outside noises to some extent (which can be good or bad depending on your situation).
As far as any issues go with these, they're minor. I'm still having some fitting issues, but my ears are weird to begin with. On some songs, I can detect the "splashiness" with the cymbals @Kazekeil has mentioned, and on other songs I can hear the "midrange resonance" mentioned by some people. Soundstage, while wide and full, does have some slight confines I can detect. Bass, even when amped (by my current portable amp at least) could use a bit more heft, but YMMV on that. I think that improves with use of a desktop amp, so maybe I just need a better portable amp.
I have no way of testing the Cipher cable even if I had one (Android user, and Lightning-to-micro USB adapters that transmit sound still don't exist as far as I know), but I'm curious to see if it can address any of the sound issues, or how the sound sig changes with it in play.
Other than that, these are perfect. These are my portable endgame now.
I grabbed these with a standard cable for a steal at $250 (+ $7.50 shipping) from Audiogon, and I could NOT be happier (unless I got i20s, which, if they correct any of the small complaints I have with the i10s, I might just do at some point far in the future).