Reviewed.com Headphones says:
These headphones are great. Not only do they provide a flat frequency response and clear sound, but their open soundstage helps provide a very realistic sound. Though these cans aren't perfect (we're still waiting on that to happen), they do field a strong performance, and should satisfy a large swath of audiophile consumers. They aren't able to go outside, but really, they were never intended to in the first place. Good show, Sennheiser!