So a couple first impressions after listening for a few minutes:
Woah, bass got really cleaned up. From my iPod and CD player, on the Shure SE215, the bass was somewhat muddy. Especially evident on "Snow (Hey Oh)" by RHCP. Everything's very clear, much more than my iPod. I've got EQ settings so that treble is up just a bit, and everything sounds great. Things sound less congested, and somewhat forwards. Vocals are great, it sounds pretty neutral, maybe some warmth to it. Certainly much harder to use than an iPod, but that was expected, and some of the problems I'm having with files (Unknown album, etc) are my fault. Listening on my SRH440s, no EQ, there is certainly a little warmth. Vocals are just slightly forwards; with the forwards vocals on the SE215, I love it. It works VERY well with the SE215. Gives a little life to the SRH440s, which are somewhat bass-light. Acoustic guitars sound great. Loving the little bit of extra bass with the SRH440 on the song "The Distance" by Cake and on "White America" by Eminem. Great separation. This is all compared to my iPod Touch 4 and Optimus CD-3450 CD player.
Edit: Just gotta say, "Sail" by AWOLNATION is addicting to listen to with this and the SE215. Controlled, strong bass, with vocals in your face, screaming "SAIL" is wonderful. All instruments separated well, may not be the best due to the SE215.