I received my T5p in the mail yesterday, and I've been listening to them almost nonstop since.
I've been comparing them to my DT770 and D7000 headphones using a variety of music, from Tangerine Dream to OMD to the Smiths to Skrillex to Baldassare Galuppi.
Bottom line: Sad to say, but they're going back.
I wouldn't call them a bad headphone, certainly. The amount of detail they reveal is incredible--they were certainly the best headphone among the three for listening "into" a mix. They also probably had the widest and deepest soundstage of the three. And, as far as comfort, I had no issues with them, even with my glasses on (the Denon still wins the award for comfort, though--but the tradeoff there is the Denon's almost utter lack of isolation).
Unfortunately, the T5p has quite a few issues (IMHO). The main one is (as others have commented) the lack of bass. Things like male vocals and snare drums seem to lack "weight" compared to the other two headphones, and the T5p seems completely unable to reproduce the throb of a synthetic bass the way that the DT770 and D7000 can--it almost seems like it's missing the entire lowest octave.
A second issue is that the T5p seems to impart a "boxy" quality to music. It's was extremely noticable when switching to the T5p from either of the other headhpones.
The final (and perhaps most important issue) is the price of the T5p. If these were $250 or even $700 headphones, I'd probably keep them, since they are very revealing.
But for $1,400, I expect a headphone that's essentialy perfect, and these most certainly aren't. I just can't justify spending twice as much as what I spent on the D7000 and 7 times as much as I spent on the DT770 for the T5p, which seems to be equally flawed as either of them, just flawed in a different way.