Summary: I purchased the MDR-V600 years ago and I love them. They were not labled "studio headphones" at the time. They are light, comfortable, and give a full rich sound. I've had my pair for more than a decade and they've held up perfectly with standard use. I missed 4 phone calls already today listening to music with them so I would have to agree that there is very little outside sound intrusion.
Summary: These headphones are the best I've worn yet. Admittedly, that's not saying much, as I've worn very few Audiophile-or-Studio-Quality headphones. However, I think they definitely can compete.
My only gripe is the pleather covering on the ear cups and headband. After two years of daily use abuse, it flakes off. Like peeling skin.