AKG K-240 MKII

To preface this, I am no expert in "high end super awesome headphones" (then again, you wouldn't be looking at these headphones for that) - however, here is my two cents:

I have replaced these with Beyerdynamic 770 Pro 80 Ohm and the difference in sound is simply staggering.

AKG's are very very flat - it is not even dependent on the mix, the bass is simply lacking - they are open headphones, so that is to be expected.
What you should also expect is a lot of sound leaking (again, expected), but don't think you can blaze some music late at night. These do get loud, but others in your household will be able to hear it.

Were it not for 770's, I would be using these still as they are very good at guitar tracking/playing, BUT - not very great in overall enjoyment of the music (well, 770's are better in my opinion).

The quality seems okay, they're not bulletproof, but they can survive a fall from the desk.

I was searching for good open headphones, but they tend to be quite expensive, so I tried this model. They sound good, clear, open, the highs are not too harsh and the image is good. Bass are there, but they are not too prominent and not too articulate.
Build quality seems ok, let's see how long they will last.
The coiled cable is nice and handy if you use them in tiny spaces.
Their main problem is the pads. The pleather ones are comfortable but this headphones sounds best with the velour, which are terrible and way too stiff. I had to buy other companies velour pads (and foam net to re-balance the highs), so keep this in mind if you want to use the velour pads.
Overall, I'm satisfied!