We spent most of our time in the Infiniti M35 Sport model. This car has one of the stronger V6 engines available, and its relatively low weight helps the V6 propel the M35 at a decent rate. The five-speed automatic transmission works well and shifts quickly. Drivers who want more control can use the manual mode, which works better than similar systems in some cars, thanks to a short-throw shift lever more akin to that of a manual transmission in a sports car.

We were satisfied with the performance of the V6 until we drove the V8-powered M45. It's almost a rocket ship, and it gives you the urge to floor the gas pedal just to feel the exhilarating acceleration. What's more, the fuel mileage is only a couple of miles per gallon lower than the V6.

The Sport models feature what Infiniti calls Rear Active Steer (RAS). Don't worry, because RAS doesn't mean the rear wheels turn to any great degree. They move a maximum of only one degree, which can't even be seen. The actuator that turns the rear wheels is powered and controlled electrically. What it does is adjust the rear toe angle in either an opposite phase going into a corner or the same phase exiting a corner, and it only operates at mid- or high-speed.

All this helps turn the car into a corner more quickly and helps stop it from sliding out on exit. Without trying two cars back to back it's difficult to determine how effective RAS is on the road. We haven't done that, but what we can say is that the Sport model proved to be very stable, handling more like a good lightweight sports sedan when purposely doing some abrupt lane changes at speed.

The optional Lane Departure Warning (LDW) system uses a camera to detect lane markings and warns a driver with a buzzer when the car starts to wander into the next lane. It only operates above 45 mph and is de-activated when the turn signals are used. It also accounts for the amount of steering wheel movement in order to avoid warnings when purposely changing lanes. The system is valuable, especially when driving late at night on empty freeways or toll roads, although it was tricked once by stripes of tar on the road and thought we were straying from our appointed lane. This is a relatively new technology, however, and at this point there's no empirical evidence that such a system reduces accidents, as there is with other systems like electronic stability control.

The M35X comes with the same all-wheel-drive system found in the G35X and the FX35. During a short drive in an M35X we didn't notice any differences in ride quality from the rear-drive models. Nor did we notice much difference in handling, though we only drove at a sedate pace. The M35X could be an excellent choice for those who regularly drive in very wet or snowy locales.

The RearView monitor system is impressive. It has a camera located in the back bumper that projects a view toward the rear onto the in-dash LCD whenever the driver shifts into Reverse. It's a great safety item as it can help a driver see objects or children behind the vehicle that are otherwise hidden from view. Infiniti's version goes one step further and displays a line on the screen that indicates the course of travel as the steering wheel is turned. It's a neat idea that works. Drivers still need to pay attention to ensure nothing is behind the car using traditional driving techniques, but rearview cameras provide the driver with useful information when backing up.