i found this interesting:
http://www.aa1car.com/library/2003/bf110322.htm
"In technical bulletin #00-05-22-002 to its dealers, GM says, "Brake rotors should only be turned when one of the following rotor surface conditions exist: severe scoring with depth in excess of 1.5 mm or 0.060 inch, pulsation from excessive lateral runout of more than .080 mm or .003 inch, thickness variation in excess of 0.025 mm or 0.001 inch, or excessive corrosion on rotor braking surfaces."
GM also says "Rotors are not to be resurfaced in an attempt to correct the following conditions: noise/squeal, cosmetic corrosion, routine pad replacement or discoloration/hard spots."
In other words, GM frowns on rotor resurfacing during what it calls "normal" pad replacement. But is any brake job ever normal? Every job is different and every rotor needs to be carefully inspected and evaluated to determine its condition when brake work is done."
on a side note, i'm ordering hawk hps's soon, and will be at least resurfacing the rotors. the last pad change i didn't, but that was with cheap autozone ones.