Probably both.
The car comes from the factory w/high ultra high performance tires that are good in dry conditions, but lose some traction in wet and snowy conditions. The car is also a RWD and must be driven accordingly. Knowledge of RWD handling dynamics such as oversteer and the affect the throttle has on handling needs to be taken into account.
My recollection of some of the incidents posted on this board occured mostly in less than ideal road conditions. Some of the driving mishpas have either been on snowy or icy roads and/or wet roads. You simply shouldn't be pushing any car regardless of engine and drivetrain layout when the road is slick.
The IS 300 is a safe car if driven accordingly to the road conditions and if the driver is mindful of the drive characteristics of a front engine RWD car.
The IS 300 is my wife's daily driver and I have complete confidence in the car's safety.
01 IJM w/LSD, 5Zigen exhaust, 5Zigen wheels, Toyo Proxes, TRD race sway bars, TRD adj. shocks (springs soon).