The Moto G has been a fantastic phone so far, except for one small bug which becomes a big irritant. If the phone is used with a headset (wired or bluetooth) and you take it off, the call volume will drop to really low levels, making it hard to hear what is being said on the other side. A reboot usually fixes the problem, but that is not an ideal solution.
The other, simpler, fix is to reduce the volume while in call and then max it. What usually happens in a situation like this is that the user will only try to push the volume to the maximum (which the phone usually is at) than reduce it. To make the fix work, you have to first reduce the volume and then increase it, making it very likely that this is a software issue than a hardware one.
Update: Motorola has released an OTA update for the single SIM GSM version for this with the 174.44.1 update that fixes this bug. There is no word on when it will be rolled out to the other models.