Powertrain performance
Most powerful sedan for under $40k. Beats any stock 4.6L Mustang, any Charger/300, and even most European sports sedans short of M5/AMG/RS or the $100K crowd.
Safety & braking
Stops on a dime, stability control is spot on even for an overpowered rear-driver. airbags all over, and spaceframe design to deform to absorb impact while maintaining passenger compartment dimensions.
Handling
Despite a bit of body roll, the chassis is very communicative, and sticks to the road.
Rear seat room & comfort
Huge back seat, and very comfortable, even for two adults and a child seat.
Front seat support & comfort
Plenty of room, good support, and do not have to squirm much on a 6 hour drive.
Fuel economy
Low teens in town, and 24mpg tops on the highway make this a less than ideal economy car.
Quietness
Can be a bit loud on startup, quiets down nicely once warm. Very little engine noise on the road unless one is aggressive with the throttle. Very little road noise under 120mph.
Audio & nav systems
No nav available due to US regs. Car was built in AUS, where they have the nav screen lower. Also would have like a HUD as in my previous Grand Prix, but dev. costs precluded it until a major refresh...which will not happen thanks to GM closing Pontiac.