To my recollection, until last week I'd never had to replace the rotors on any car I'd ever owned. The reason I replaced them on the HHR was (what apparently is a common problem on HHRs) warped rotors....resulting in a vibration in the steering wheel when stopping from from high speed .....I suppose just having them turned would have helped but some people on the internet were having the problem every 5-10K miles....

Must have been a batch of rotors on HHRs made from crappy metal .....