Got mine today as well. My first impression was, "Wow, this thing is tiny!" I know everyone mentions the size, but for some reason, I was still expecting something bigger. This thing is about the size of a pack of cigarettes though - almost gets lost on my mess of a desk.
With a couple hours of testing, I've discovered that the E10 is a very different animal on my two current sets of headphones - VSonic GR-07 and Turtle Beach Earforce Z2 (yes, I know, it's not that great).
I initially listened to the E10 through the Z2s, and my first impressions were (surprise, surprise) not very good. I couldn't detect much a difference between my laptop's headphone out (Realtek HD Audio) and the E10. If anything, the laptop's headphone out sounded slightly clearer. The bass boost turned the bass in most tracks into a bloated, muddy mess - needless to say, I wasn't impressed.
However, when I plugged in my GR-07s, that all changed. There still isn't a huge difference, but compared to the laptop audio, the E10 tightens up the sound a bit and clears a little bit of distortion. The bass boost is actually useable and adds a nice bit of punch to the IEMs when called on. Unlike ClieOS, I am getting quite a bit of hiss coming in at around volume 3, even at low gain. This is likely the GR-07s, though I don't have anything else of any quality to compare them with yet.
Just for fun, I plugged in my old Sennheiser CX500s that have been collecting dust since I got the GR-07s. Damn, I'd forgotten how bass-heavy those were. They're so bassy that I can't stand to use the bass boost, even on bass-light songs. Compared to my computer audio with these, the instruments are clearer and sharper, though vocals don't change much.
So I guess the lesson from this is that not only does a good set of headphones deserve a good source, but a good source also deserves a good set of headphones. In other words, don't expect this to make your ibuds sound like UM customs. But then, you all probably knew that already.
I'll post some more impressions later - I have HD555s due in tomorrow and FA-011s coming (hopefully) next week, so maybe I'll see a bigger difference with those.