I drive it hard, but not abusive. The same way I drive my own car (though I don't drive that way all the time).
If it's a stick shift, then I'm letting it run out in 1st and 2nd, testing the reaction to flooring the throttle with the engine in 3rd at 20-25 mph, looking for brake fade, seeing how the car handles rapid transitions, finding out how it reacts to hard acceleration out of a corner (this is particularly important for FWD cars with open differentials because they generally suck at it), seeing how well the pedals are set up for heel-and-toe downshifts, and seeing how well the engine can be "blipped" during double-clutching (some modern cars do not close the throttle plate quickly which is good for emissions, but terrible for double-clutching because you want the engine to return to idle _right now_ when you take your foot off the accelerator).
What I am not trying to do: Spin the tires in any way, shape, or form; dump the clutch; speed-shift, or anything else that is damaging to the mechanicals of the car. It's perfectly possible to drive a car fast and hard without causing undue stress to the componants.
ZV