I've had the HP50's now since Nov 5 2013, it's now December 16th.
I live in Calgary, AB but had to drive to Edmonton to purchase mine, nobody in town is carrying them.
In a nutshell, I'm crazy about "British" Sound. It's flat, accurate and never sounds strained.
I have a pair of Grado SR 60's which I bought just to keep the neighbours off my back at night and a superb pair of Shure SE535's.
Those are a significant bit pricier than the NADS.
In a word?
These don't sound anything like and American Headphone.
They open up a 'room' like nothing I've ever heard.
Imaging isn't so much IN your head as it is all around it.
They are uncanny. Pun intended.
I compared them, QUICKLY, to the KEF M500's back and forth over and over again and these feel, fit and sound very different.
The KEF's fall off your head if you tip it forward.
I found the NADS dug about a teaspoon more detail out than the the KEFS but the fact that they were sealed, superb and would stay on your noggin' settled the decision, for me.
I bought them based on this REVIEW, that I'd only read the night before.