I take my torque wrench with me to the tire shop, always .. unless it is Discount Tires (tires.com), they always hand torque them.
If the shop uses an air gun to tighten your wheels without a torque stick, they will wrap your rotors, because they will exert uneven pressure on each lug nut, so your rotors are not straight anymore, you can tell that from 2 things, vibration at highway speeds and also your steeting wheel will shake when you hit the brakes, if this happens to you, I would highly recommend that you bitch about it and get them to replace your rotors.
The best thing is, to always hand torque them with a torque wrench to your manufacturer specs, 80 to 90 ft/lbs is usually good enough to passenger cars.