Purchased a pair of D600s off the FS forum here at a significantly discounted price. Just got them delivered today.
A few hours in and comfort is very good; the build is more solid than I imagined. I'm actually quite pleased with them in regards to aesthetics. They are also significantly larger and weightier than I had expected from seeing pictures. Can't see myself using these very often in a portable fashion, if at all. Worried listening to these will be fatiguing, will see how things go.
Definite emphasis in the lower end of the headphones. Can be very enjoyable with certain songs. I let a bass loving friend of mine try them, and she absolutely loves them and has pronounced them her favorite to date. This is after her having heard stuff I've brought to her like the HD 600, HD800, LCD 2, Paradox. I can imagine these being absolutely wonderful for casual music lovers who like the mainstream music of today.
Will probably end up keeping these for occasional use when I want a bass kick, and to let those coworkers/friends of mine that like heavy lower end accentuated headphones borrow. At the price I bought them for I feel they were a worthwhile pickup. Didn't even try to EQ them to a more neutral sound, tried a few EQ settings on the J3 and actually ended up coloring them further for a more enjoyable "unnatural" sound.
A fun pair of cans.