BMW's all-new 745i is so different from the previous model that it forces you to rethink the definition of a luxury performance sedan. With a radical new interface between the driver and vehicle, called iDrive, and bold styling that has met with mixed reviews because of the unusual trunk lid, the 745i challenges conventional wisdom with a new paradigm.

For the wealthy buyers who can afford cars in this segment, state-of-the-art technology is what's expected. The new 745i is so complex that touching on all of its features is nearly impossible in a single review.

First, the styling. When I saw the Z9 coupe concept at the Frankfurt auto show more than two years ago, little did I realize that its unusual shape was a precursor of the next Seven-series sedan. Despite the fact that this car is actually larger than the older Seven-series, it looks smaller, leaner and more athletic. The body fits like Spandex. Subtle spats over the huge 18-inch wheels shout muscle and performance, while its simple lines and lack of extraneous trim speak elegance. The raised trunk lid, which has garnered some negative comments, is there to improve aerodynamics and increase trunk capacity. Although the look is different, I grew to like it immensely.

Second, the iDrive system, where the computer age meets the automobile. The vehicle is started by inserting an electronic key into the dash and pushing the start/stop button. Instead of having the gearshift lever in the center console, it has been moved to the steering column. In its place sits a large, round knob that controls nearly all of the 745i's accessories: navigation system, audio system and climate control. The knob is a joysticklike controller. You rotate, push and tilt it to make various selections that are displayed on a color LCD screen in the center of the instrument panel. iDrive can be frustrating to learn and use. I spent 10 minutes with the manual just trying to program new radio stations. Once I figured it out, however, it was reasonably easy to use, but after a week with the car I think I still prefer knobs and buttons that are more intuitive to use. Fortunately, the system can also be operated by voice commands.

BMW contends that iDrive simplifies the layout of the instrument panel and console, and it does. The 745i's interior design is most striking. The ample use of matte-finished wood and brushed aluminum trim pieces gave the interior a high-tech, Danish-furniture look that was restful and elegant. The front seats were extremely deep and comfortable, thanks to the fact that every section is adjustable. Control knobs are located on the side of the center armrest, a placement I found more awkward than conventional locations on the door or lower seat panel.

One change I liked was the placement of the gearshift lever on the steering column. This small lever, not much bigger than the turn signal, electronically selects the proper gear. It is easy to flip with your finger, and its oper ation quickly became second nature. Engaging Park is done with a small button on the end of the lever. The 745i forces the driver and passenger to learn new habits for everyday functions, but the comfort level rises once this is accomplished.

Innovations are not limited to the iDrive system. Every facet of the vehicle has been changed or upgraded. Talking about this car without inducing technological overload is nearly impossible. The 4.4-liter, DOHC V-8 uses an electronic accelerator pedal, and the Valvetronic system is capable of varying valve lift so much that BMW says the valves effectively become the engine's throttle.

Double VANOS steplessly varies the timing of both intake and exhaust valves for optimum performance at low or high engine speeds. The system allows an ultra-smooth idle as well as robust acceleration. This engine produces 325 horsepower, but you would never know it until you mash the accelerator flat to the floor. In an instant this velvet-smooth luxury car turns into a tire-scalding bullet that pins you back into the seat with a race-car shriek from its exhaust. Dr. Jekyll, shake hands with Mr. Hyde.

A six-speed automatic transmission is a first, as well. Small buttons on the steering wheel enable the driver to hold the transmission in gear, or shift to a lower one. Steptronic shifting will be offered on subsequent models, but it is not available on this car because of its impact on fuel economy.

The suspension is nearly as complex as the engine. Active Roll Stabilization uses two active anti-roll bars, instead of one, to counteract body roll as the car enters a turn. Various sensors and an oil pump react to forces placed on the vehicle in a turn and limit how far the body leans. On the road it reacts as if were reading your mind. As you nose it into an exit ramp, it remains fairly flat and the tires grip tenaciously. Driven hard, it responds like a four-door sports car instead of a luxury sedan, just as you expect a BMW to do.

Front, side and head-protection airbags are standard, while side and head-protection airbags for the rear are optional.

Because it is so dramatically different, the 745i requires an open mind and a willingness to learn its intricacies. After just a week with it, I was smitten with the styling, power, handling and elegant interior. I never quite came to terms with iDrive, but at least I could make it do what I wanted most of the time. It may be an acquired taste, like exotic food, but once you get familiar with it you want more.

The base price of our test car was $67,850. Options included the convenience package, cold-weather package, premium sound system, rear side airbags with head protection, rear sunshade and parking sensors. The sticker price was $74,395.

Four years or 50,000 miles.

Point: The all-new 745i is a redefinition of the luxury sedan. Aggressive styling is boldly original for a car in this class. The engine boasts 325 horsepower and the sumptuous interior has all the comfort and convenience one expects in a car that costs as much as a small house.

Counterpoint: The iDrive system brings a computer interface to the automobile, and it takes a while to get even partially comfortable with it. Despite the wow factor, I think simple knobs would still be my preference, but then that is the price you pay for being on the cutting edge.

Engine: 4.4-liter, 325-hp V-8
Transmission: automatic Rear-wheel drive
Wheelbase: 117.7 inches
Curb weight: 4,376 lbs.
Base price: $67,850
As driven: $74,395
Mpg rating: 18 city, 26 hwy.
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