Pros: Fun, Musical to listen. Smooth and detailed. Very comfy and non-fatigue headphones.
Cons: Bass maybe boosted a tad too much. Ears get hot in hot weather (~33°C)
Here's my D600 out-of-box impressions.
Received only yesterday and paired with the ODAC/O2 as my laptop rig, the bass is the first thing that captures your attention. In some songs, like David Guetta's, the D600 would deliver great and deep bass, slightly more than HFi2400 even, IMO. However, the bass is always nicely controlled and tight, not intruding into the mids. The D600s have both ample quantity and quality bass, maybe boosted in the midbass IMO; but not overly emphasised.
The mids are fine and smooth, but sometimes they lack a bit a bit of volume especially if you have listened to mid-centric headphones; but overall are still smooth. Prefer the mids of my srh1840 in that relation.
Treble is clear and detailed, non-sibilant and non-fatigue.
Soundstage is deep and good separation. The Imaging is quite similar to that of HFi 2400s are known for IMO.
IMO the D600s are fun, fast attacking and falls into the musical headphones category. The Denons not do sound grainy at all and are detailed and smooth. It shines the most at pop, rock, rnb, electronic IMO.