Device reception is fine, at least when calling a land line. Calling other cell devices, that is variable. It has nothing to do with the Z10 phone or any other phone. The biggest issue, whether it is 2G, 3G, or 4G or whatever, the call quality has more to do with the provider's equipment. If the transmission is stifled by the quality that is available with the transmission then the connection is going to be marginal. All carriers have this issue. They need to upgrade their transmission equipment to move data better, but, they don't do that. Don't blame the phone.
I went from a GNex to the Z10 for that exact reason. Don't need a ton of apps, but do need great connectivity. The Z10 works perfect for me. Better signal strength and excellent voice connections regardless of land line or wireless. If your looking for a dependable, good phone, the Z10 is the one.
I've had no issues with my Z10. However, Z30 is coming soon with Paratek technology in the antenna that is supposed to dramatically increase signal strength AND reduce battery drain.