Mine has some earpiece static, but it's not reason to return it. I can only hear it in a quiet room, and only if I place it really close to my ear.
As for the squeaky buttons, mine sort of does that depending on how I press it.
My USB port is fine I think.
What do you mean by "random grinding from camera when in use"?
The earpiece static was noticeably loud.
No matter how I pressed the buttons they would squeak.
The USB port was so loose that the metal inside of it moved outward when taking the USB cord out of the device.
The camera would fail to focus, grind, fail to focus, grind until after about 30 seconds or so take a pic and continue grinding. Only way to stop this was tapping on the back of the device to free the auto focus mechanism.
My argument for these replacements is that my GFs N4 is flawless. The buttons are solid and aren't recessed like most of my replacements. No squeaks, almost no earpiece static and no random popping noises.