I have to say I am a little underwhelmed thus far with my E17. I've only had it a couple of days and isn't really bad, just not as earth shaking as I was hoping. Using it with my Laptop via USB it definitely improves the sound of my music collection but doesn't seem to be as noticeable with movies ripped at around 1-2GB.
Using it with my iPhone it definitely improves the sound but to be honest I still think my Aud-5X CIEMs sound better straight from my Rockboxed Clip+. The clip just seems to have better extension, particularly in the sub-bass department which is very important to me. The only downside to the Clip+ for me is the user interface (I tend to flick around songs rather than just let an album play) so I was hoping the E17 would give me the same sound but with the iPhone touch interface (using either the standard player or panamp). Sadly it hasn't so I think I now need to decide if I'll keep it just for my laptop or sell it on here.
Don't get me wrong, the E17 does sound a lot better than the standard iPhone but if I prefer the sound of the Clip+ then the extra weight and bulk is hard to justify.