First of all, the build quality is excellent! You can clearly see that durability and serviceability were the main priorities when designing these headphones. I'm so happy to see that in today's world of disposable consumer goods someone still makes a product where nearly every component is replaceable. I wish more manufacturers did that...
Once I put the headphones on, I immediately noticed how soft the earpads were and how well they isolated from the outside noise. The headband didn't feel great at first but, after some tweaking around, I found the position where it felt comfortable enough for extended use.
Now, the sound! As soon as I turned on some jazz, I was blown away by how big the sound stage was. It didn't even seem like the sound was coming from the headphones. Instead, I felt like Don Ellis was performing "Whiplash" in my very own kitchen! I most certainly didn't expect that from closed-back headphones. Furthermore, the level of detail is mind-blowing! Whereas on all of the headphones I'd had previously the drivers felt stiff, as if they couldn't move quickly enough to reproduce the amount of detail contained in a high quality audio recording, the Beyerdynamics impressed me by unveiling the intricacies I hadn't heard before. Their superiority is especially apparent when listening to vocals. Those extra details really help convey the emotions in the singer's voice.
If you're looking for a pair of relatively inexpensive high quality headphones, then you should definitely put Beyerdynamic DT 770 Pros at the very top of your shopping list!