Funny you should ask -- i just got the HP50s today and unboxed them tonight. I've been trying them out for the past hour or so. My initial impressions are that they sound very good but will probably be a no go in the comfort department. Unlike the Momentums, the discomfort is not so much at the ears but at the "Frankenstein" band exerting pressure in a concentrated area at the top of my head. It's a shame. I can't seem to find a good closed back option which fits me well.
I compared the HP50s to the HD598s and preferred the former. While the HD598s sound good, I've never been wild about how they sound and wonder if an amp/DAC would be the antidote. I have to decide whether I will keep them or return them by Wednesday. On The Sound of Silence by Simon and Garfunkel, the voices sounded so much closer and robust through the HP50s (like the folk pair was right there) than they did through the HD598s. I wonder if it's a closed back vs. open back thing. Of course the HD598s are so darn comfortable. I just wonder if some gain will make the sound much richer, not to suggest it necessarily sounds bad now, just not entirely what I'm looking for.
As for work letting me try out my headphones, not so much ...
A few days ago, I had a sit down with my boss. He was alerted by corporate to my high-end headphone spending habits. He was understanding but it behooves me to throttle back for now.