Not only is there little leakage, but the sound isolation is quite good. The isolation is significantly better than the Sennheiser 280s, as well as the comfort. (I own both.) The Beyerdynamic are also the best sounding closed headphones that I own. I find that they have better highs and a more pleasing sound than the Sennheiser 280s, and are just as detailed.

I second Beyerdynamic. I have a pair of DT 770 Pro at home and DT 231 in the office. A bit pricey, but great quality.