How long have you been using it daily? Two months at four hours a day will squish the pads enough too far. On very new pads, yes the treble is detailed, extended, and most importantly, smooth. Songs like Fantasmic, Astral Romance (I prefer the remix with Tony Kakko) and 10th Man Down are just fantastic on these; if I hadn't heard them on Stax (407 and Omega), K1000, Sonus Faber Guarneri and Aurum Cantus Volla, I'd still be getting goosebumps from the HD600. For the money though I'm hardpressed to like anything else.
My ear pad still feels like new. On weekend, more than 5 hours usually. On weekdays, around 3 hours depend on my day. Though I'm not listening to music, I wear for gaming and surprisingly accurate and fun. Playing Devil May Cry with those metal songs while hack and slash turn me on. But too bad, doesn't comfy as Beyer pad, the most comfortable I ever tried.