The Sennheiser HD-280 Pros are, quite frankly, the best set of professional headphones which I have used in terms of sound quality, performance, and comfort.
The sound from these headphones is phenomenal. Thanks to the oxygen free copper cabling used in the 280, the signal is very clean. The bass is precise and defined, with virtually no low-frequency sounds being muffled or blatty. Higher frequencies do not hiss or squeal, and are produced flawlessly.
Once you begin playing music through these phones, outside noice is reduced tremendously, accentuating your music and lessening outside noise. The HD-280 Pros use passive noise attenuation. This means that in order for them to cancel outside noises, they must be tight. A significantly larger force than most headphones is applied in order for these headphones to accomplish this. Luckily, forgiving padding is used to reduce the amount of pressure applied to the user. Passive noise attenuation also means there is no artifacting from electronic noise, meaning the only sound you'll hear is from your music; a feature which is not true with most consumer headphones.
The 280s are, in fact, quite large; meaning they are slightly cumbersome to use in public places. These headphones are more atuned to a studios audio sampling needs, or for a long airplane flight. They fold together tightly and compactly for easy storage, but I do not reccomend tossing them around in a backpack, they are'nt made of titanium.
Overall, The Sennheiser HD 280 Pro is a fine peice of equipment, perfect for professional use in the studio or for just getting the best sound quality from your music, period.