I bought these to replace the horrible white set that came with my company iphone4. My phone is primarily a business tool and I bought this mainly to use as a handsfree kit at my home-office, as I need to be on the phone a lot and type or write at the same time. From this perspective, it is absolutely fantastic, the incoming call quality is incredibly clear and loud, to the extent that I rarely have it on max volume because it is uncomfortably loud (and I mean pure volume, NOT distortion). I rarely get callers saying they cant hear me and on the odd occasion it has happened, it is quickly remedied by talking a little more towards the mic.
I should say that I am definitely NOT a music buff and mainly listen to my music in my car or via a Dock, but that said the music quality (to me) is also very, very good. Again, I never have it on full volume although my hearing isn't the best, as it just doesn't need to be and quality is crisp and clear. I'm afraid I dont know enough about it to go into depth and bass etc. but it sounds sharp and rich to my ears! Although probably standard with most other decent makes/models, you also get 3 different sizes of earphone cover for maximum comfort. Cannot fault this unit in any way.