Like Inks said, there's something about them. Usually I like bright phones and I'm quick to return something if it doesn't meet my demands (like the Klipsch S4, SOL Amps, Philips 3580, Ultimate Ears and a bunch of others - I've returned so many headphones that stores have my picture hanging up behind the counter). But for some reason I just kept listening to these and now my other phones just don't sound right.
As for the ER-6i's, gnarlsagan, I spent a lot of time ensuring I had a good seal - even so far as ordering the two-flange tips. The seal was so good that the sound of my own breathing was like the sound one would hear while scuba diving. I found that I was spending a lot of time trying to jam the phones deeper into my ears to reclaim the missing bass.
I did love the rest of the frequency range, though, and it almost made up for the bass.