I've had the odd rivet go a little loose on the Shimano rotor, just support the bottom of the rivet on a solid surface and tap the top of the rivet with a hammer to tighten it.
Sent back an old Etrex legend, it was seconhand when I bought it, screen had died, they replaced screen and the rubber surround also the toggle switch all FOC.. I would say there service is excellent..
I have optilabs glasses with varifocals, very pleased with them, they made them with the reading focal part slightly lower than my normal glasses as they are used more for distance than reading.