This really applies to any unlocked phone that supports HD audio and doesn't necessarily apply only to the Z3. It is a bit of a concern for me buying a phone that's not actually sold by the carrier. With HD audio just around the corner for many areas, whether or not the HD audio in the Z3 gets supported on your carrier is very dicey. I'm on AT&T and seriously considering this phone. AT&T already has HD audio in a few areas and on a few phones. However, although the Z3 is capable of HD audio, using an unlocked phone on AT&T (or other carriers that have this capability) is no guarantee that your phone will have the HD audio implemented on a carrier that really doesn't sell or support the phone. At least that's my understanding of the issue and I'd welcome other thoughts on this.