I have Sony's MDR-CD580 headphones. I've had them for a few years now and I absolutely love them (great sound, very comfortable). One consideration I think is usually applicable to notebook users is how much sound escapes the headphones. If you work with people around you, you might consider "sealed" headphones that don't allow much sound to escape. However, headphones that allow sound to escape are generally considered to deliver better quality. I only know this from researching them the last time--I don't know that I could tell the difference.
However, there are other great headphones out there like Koss, Grado and Sennheiser (all I think considered better than Sony). In fact there are whole communities dedicated to the things. Try:http://www.headphonereviews.org/