We spent most of our time in the 2006 Infiniti M35 Sport model, but we also drove an M45. Lower weight helps the V6 engine provide enough power to propel the M35 at a decent rate. The five-speed automatic transmission works well with quick shifting. Drivers who want more control can use the manual mode, which works better than in some cars as the shift lever has a short throw more akin to that of a manual transmission in a sports car.

We were satisfied with the V6's performance until we drove the M45 with the 335-horsepower V8. It's a rocket ship providing exhilarating acceleration. Not surprising, as Infiniti claims it is the most powerful V8 among its competitors. What's more the fuel consumption is only a couple of miles per gallon worse, no doubt because the V8 is not working as hard. Unfortunately it ups the cost by almost $7,000, compared to the M35 models. (BMW and Mercedes buyers also face a big premium for the more powerful engines.)

The Sport models feature include what Infiniti calls Rear Active Steer. Don't worry it doesn't mean the rear wheels turn to any great degree. In fact they only move a maximum of one degree, which is unnoticeable visibly. 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. That 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 it is in reality. All 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. In addition it detects the amount of movement of the steering wheel in order to avoid giving out warnings when one is purposely changing lanes. The system is probably a good idea especially when driving late at night on empty freeways or toll roads.

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 driving in slippery conditions.

The RearView monitor system is impressive. It has a camera located in the back bumper that projects a view toward the rear view onto the LCD for the navigation system. 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 as it displays a line on the screen that indicates the course one is headed along as the steering wheel is turned. It's a really neat idea that works. Drivers still need to pay attention to ensure nothing is behind the car, however.