Only used briefly so far. Sound is perfect as you'd expect although they don't completely block outside noise so if you're in the gym listening to something quiet (as in classical) then the music playing in the gym will be heard over it quite badly. For normal/louder music this wasn't an issue.
Comfort, worn them for an hour and seem ok although I'd prefer a more in the ear feel. Will take for a run next.
I will note that a lot of people complained about audio lag for video viewing but there's none that I noticed in both Netflix or YouTube. Bought mine for $206 not sure if I'd be willing to pay much more for them.