On mp3store forum (polish site, google translate it) there are some reviews of them.
I (still) have them, but I have not used them much (but for instance I've used a lot Pro80 and HD6000, even HD5500 seems to be better),
As for flaws, I would say:
- The bass does not go down (there is not much of subass), they are a little bit mid-bass oriented (but I would not call them muddy)
- The highs are present, but they also don't extend that much, and are a little bit ragged (not smooth), but they are not sharped compared to Hi2050 or even Pro80
- The soundstage is wide, the instruments on the left/right side seemed to be big (too big), but overall placement and shape is not that good (still there is that wow factor)
- For me there is a little problem with the mids (probably related to the 3 things above, that is why I did not use them).
Those are kind of reverse of Pro80, they would be good for softer music, or instrumental/classical if you are willing to sacrifice the sharpness of sound,
saying it otherwise they are good if you want to relax to music.
Generally the balance is ok, and they provide big sound.
I would add that as I mentioned mainly 'flaws' my opinion will seem more negative that it is needed to be (but on that forum I mentioned above, there are a lot of people who like them much, espacially as go away cans, like in oposotion to more analitycal sound)