I've had a similar experience as JaZZ. I bought these instead of the Sony 3000 on the recommendation of fellow member joelongwood (not a reflection on the Sony but because joe thought I'd prefer the Beyer with my Sugden amp). In my message to joe about my initial impressions, I wrote that the dt880 is definitely more revealing than my Sennheiser HD600 (with original cable), has more snap or dynamics, and better separation of voices and instruments. With more break-in, especially after using a Purist Audio Design System Enhancer Rev. B (break-in disk), the treble smoothed out nicely. As JaZZ mentioned, the soundstage seems to be slightly wider which, for me, means the angle of sound in my head, the V if you will, drops more toward my ears.
The increased resolution and snap make listening to the Beyers more fun for me and I haven't gone back to the 600's for any extended length of listening. I plan to try some Cardas or Equinox cables for the 600's soon and it will be interesting to compare these headphones again.
BTW, the Beyers are very comfortable, but I still find the 600's slightly more comfortable, perhaps because of the oval versus round shape. As always when discussing sonic impressions, YMMV - the 600's are great headphones and their refined sound and comfort level will be preferred by many. Hope this helps.
Adam