I finally got my own pair in.
And wow! I had some ears-on time with these before, but now that I owned them... I have noticed that:
1) Depending on the track, the cans may sound cold/analytical or warm/dark. It's like magic! Like Audio Technica stuck an EQ in there or something. And it almost always "EQ" the track just right.
2) These are so very revealing. They are even more revealing than my DT880!
That said, as far as sound quality goes, I have noticed that...
Bass: given the right track, bass on these has authority, texture, and control the kind of which I have only found on cans much bigger! At times, I feel they completely surpass Denon D2000 and approach LCD-2 level, which is... crazy, to say the least. And bass is definitely on the fast side. HD650 and DT880 feels slow in comparison. But the presentation has no depth (at all), so bass is less layered. Still, I don't think anyone can ever say these cans lack bass.
Midrange: also given the right track, midrange can be warm, up front, and resolving. It's funny, but I think these completely put DT880 and HD650 to shame where mid is concerned. It's liquid smooth regardless of the track, and I can easily hear things that I could not pick up with the DT880 or HD650. This is the first time I have heard mid this good!
Treble: I find the ES10 has plenty of sparkle. In fact, I think it has more sparkle than my DT880, which is famous for being bright. But what's amazing is that it has insane control. I could not detect any sibilance regardless of what tracks I put on, yet I can clearly hear compression artifacts at frequencies that my DT880 could not pick up.
Soundstage: not as big as DT880 or HD650, but definitely not small. In fact, it's moderately sized for closed cans, and somehow, I find that there is more depth and layers than I expected. This layering effect almost rival DT880... though DT880 has the advantage of being semi-open, and thus has more "air".
Instrument Separation and Imaging: it puts DT880 600 Ohm to shame. What more can I say?
Overall, I'm enjoying these very much!