I have waited a year to write the full review to these headphones (over a year, in fact. Ordered them on March 10th, 2010, date of writing is April 14th, 2011).
The reason I decided to wait a year to write a full review is due to the fact that I find headphones of this price need to be given a long period of time before the fulfil their true worth (given that it is in many ways quite a large investment).
After a year of incredibly heavy usage (at least 3-4 hours a day for over a year) I can find no fault in them, they are the same as they were when I first unpacked and listened to them. The bottom end is still as well rounded and clear as before, the top end (perhaps a bit bright for purely 'entertainment' use) is clean and well formed and the mid-range is crisp and unmarked by distortion.
What little wear is done to the (replaceable) around-ear cups, and in reality that 'wear', is merely cosmetic and could have been easily avoided by a little more care in use.
Surprisingly, for such high quality (professional standard) headphones, I find that they are not in the least bit tiring to use for very long periods of time, and I have little to no fatigue after long stretches of use.
Truly the greatest pair of headphones I have ever used, and a great investment if you find yourself (like I did) burning through the mid/high range hi-fi headphones (Sony, Sennheiser etc...) quicker than is fiscally comfortable.
The frequency range (if you're interested) is:
After doing a bit of testing (using Fruity Loops and other software) I discovered that they do struggle at both 5Hz and near 30,000Hz.
They do however comfortably go from 8Hz to 26,000Hz