I've had mine fitted for a 3 weeks now. That's means 3 weekends of skifield access roads. Unlike most of the US skifields many of the NZ skifield access roads are gravel rocky rutted steep roads that wind up the face of a mountain.

The one at Ohau [http://www.ohau.co.nz] was the worst i've encountered, obviously hadn't been graded in a long time, and on some portions the gravel had worn away leaving just bear rock to drive over. To give you some idea of the shaking:
1) I passed some cars whose drivers decided the conditions warrented a speed of 5Kph
2) The center caps of my alloy wheels needed tapping back into place every day
3) The handling of the car on the way home had noticably detereiorated due to the pounding the shock absorbers took
4) One american tourist we passed asked how much further to go and if the road got any better. When we said 3/4, and no, he turned around and left.

Anyway, the empeg has never skipped a beat, unlike some of the cd players with 20 second buffers i previously used. Obviously the long term effects are unknown, but you've got robust laptop drives, shock absorbing mounting, and the fact that the big cache allows the drive to be spun down most of the time working in your favour.