I just got my HP50's today and may I say it sounds absolutely wonderful. Unfortunately I don't own any other headphones of similar type to do a comparison so I won't comment on the sound (I like it and that's all that matters )
Comfort wise, I believe they are excellent. They fit me rather well, the earpad size is fine and also its nice and soft, it's quite light and the headband is comfortable although there is a slight yet concentrated pressure at the top of my head (this may not go well with some people). Build quality wise they feel quite sturdy, the fit adjustment for the headband worked perfectly on mine.
For my first full sized headphone, they are awesome. Great for metal music.
Congrats on a great first choice!