I agree. There is great separation with the etys, amazing detail although a little bass shy. The soundstage is strange, it can be open and wide on a good recording but the stage is always inside your head, like you are not really hearing the music in the same way as with their full-sized counterparts. It is as if the sound is coming from inside your brain. Strange but good.
Some actually prefer a "soundstage" placed inside your head to a more traditional speaker setup. I don't understand whats wrong with these people.
I find all IEM's have the tendency to have a negative soundstage, placed inside your heard. Some do it to more or less extent, however. The UM2's and Super.fi 5 are a bit better, while I feel Shures and Etys are a bit worse in this regard.
Granted, it's small. Nothing like the difference between headphones in general and speakers. You can't top speakers, but get very close to matching them probably with an AKG K1000.
Soundstage is 3D, or you can call it holographic imaging.
Left to right stereo separation is the first dimension. IEMs can do this fine, although everything is inside the ehad.
Height is the second dimension. IME I never experienced much soundstage height with IEMs.
Depth is the third dimentsion. It is pretty hard for any headphone to project any soundstage depth, not to mention IEMs.
When you have 3D soundstage, not only can you locate the instrument location, you also feel the air around it, as well as room ambience. Even the best IEMs like UE-10 fails pretty short of this goal.