While I'm very unlikely to get any of these new headphones for myself, I do always have friends looking for open and/or portable cans. Especially with open headphones, there's always something not quite right...
Sennheiser HD598, 558 and 518: the most agreeable overall sounds and comfort levels, but too expensive at local retail
Audio Technica AD_x series: fussy headband, no bass
AKG K612: impossible to drive on on-board / portable sound, splashy mids/highs makes it intolerable for long listening sessions
Beyerdynamic DT880 / DT990: sharp, close to piercing highs
And the list goes on and on and on...
So here's to hoping the HD599 will be more reasonably priced at MSRP than the HD598.
Eh, who am I kidding?