I originally got these headphones because I was looking for headphones to use both for late night listening (in an apartment complex with thin walls) and travel.  So for me isolation was one of the first things I was looking for, and these headphones deliver that in spades.  Unfortunately, it comes at the cost of a fairly tight fit around the head.  Not enough to really be uncomfortable (I've used these headphones for hours on end), but enough to be noticeable.  The headphones are fairly bulky in size, but fold for travel, and I've found them to be much more durable than I was expecting given the reviews -- after several years and numerous airplane trips, the headphones have suffered no visible damage. 
 
I listen mostly to classical music, and I found the sound to be quite good -- everything comes through clear and clean, and I have no problems with any particular range in the spectrum.  Given my needs (high isolation with decent sound), these headphones were exactly what I was looking for.