I've heard some things I hadn't heard before, both good and bad. For example, one of my favorite discs is a recording of Jacqueline du Pré and Daniel Barenboim playing Beethoven cello/piano sonatas. It was, alas, a live recording, and I've always been annoyed by the coughing, but now it sounds worse because it sounds like I'm right there in the audience. The coughs are more detailed. Ug. Also, it feels as if the music is mostly in the right channel, as if I were sitting and looking straightforward, with the musicians playing to my right. It's clearly a quirk of how the thing was recorded/mixed, for the perceived imbalance is not present in other recordings. Also, during a recording of Helene Grimaud playing a Brahms concerto, I hear something that might be her breathing, or maybe the sound of air being pushed out of her seat cushion if she were maybe moving around...I don't know what it is, but it's there. Never heard it before, not on my DBA-02 Mk 2 IEMs or my un-amped DT770/32s.
In another recording (The Magic Flute), I thought I was hearing a problem with higher registers because the female soprano voice during "O Tamino Mein" didn't sound great in comparison to the male tenor, which sounded phenomenal. But on other recordings (Natalie Dessay singing Mozart's Mass in C Minor, for example), the soprano is terrific. So, either the woman on my magic flute recording isn't that good, or maybe she just wasn't mic'ed as well as she should have been?
The good news is that many things clearly sound better. I'll keep listening so that I can pin down the highlights, but in general I notice more detail, more sonority (I hear better the vibrations of cellos and of bow against string), and some of the voices I've heard really just shine, like Dessay and that tenor in the Magic Flute. The big fourth movement in Saint-Saens' organ symphony is gloriously detailed yet powerful. I love the bit at the end when the organist sounds like he's just stomping on those foot pedals for all he's worth...
One danger: I'm clearly playing my music louder, really because there's more to listen to. It's like when I first saw an HD broadcast on a good HDTV and wanted to get right in front of the screen so that I could examine all the new details.
Oh, and for the record, my Schiit Magni 2 (the non-uber version) clearly handles the 600 ohms DT880 well. I won't/can't argue that a different or better amp would be better...I have nothing to compare, but the Magni is certainly up to the job.
The real danger: because of having read so many reviews on this site, I'm eager to try other cans, not because I think the DT880s are deficient in any way, but out of curiosity and the knowledge that the sound signature of other cans might be more pleasing to my ears, even if those cans are not 'better.' I'd love to get my hands on the HD600s, the 7xx, and the Fidelio X2...