I can only agree with all the previous reviewers about the sound, built quality etc. The bottom end, particularly, is phenomenal. It's punchy, tight and very detailed. The headphones are incredibly comfortable to wear. Even after several hours you won't feel fatigue or discomfort. As for the volume: Most people commenting on the loudness of these headphones have the 250OHM version. This means that tiny headphone amplifiers like those of music players and smart phones will not have enough power to get these headphones really loud. There is now, however, an 80OHM version which I would recommend if volume is a concern for you (80OHM being less resistance so the iPod/phone etc won't have to work so hard to achieve high SPL levels).
However, on a practical note I have worn these headphones on the tube and did not have to turn my iPhone 3G up full in order to enjoy the music. Because the design is closed, covering the entire ear you won't be polluting people in public places either even if you turn the music up. Please keep in mind that these headphones were built for professional recording studios and sound stages etc where the equipment is capable of driving a 250OHM load easily. If that's not how you will use them check out the 80OHM version instead.
One thing I would like to add is that if you travel a lot you might want to check out the Sony MDR 7506 - Headphones ( ear-cup )
. Whilst they are sonically not as amazing as the Beyers they still sound very good and cost £50 less.They come in a pouch and fold up easily which makes them very practical. They are my preferred choice for traveling.