If it ain't broke, don't fix it. Or at the very least, don't screw it up. That's the mantra that must've been hanging in banner form at Infiniti's design headquarters when the time came to redo its popular G series luxury sport coupe. The outgoing model looked great and was a joy to drive, a sort of middle ground that could be viewed as either a more civilized Nissan 350Z or a more hooliganized G35 sedan.

Thankfully, the new 2008 Infiniti G37 follows the same formula. It looks great (albeit in a more voluptuous sort of way than the original), is even more of a hoot to drive and more deftly serves as either a sports car or luxury car, depending on its driver's mood. Oh, and lest we forget to mention, it now sports a larger, 330-hp engine. In other words, Infiniti definitely didn't screw it up.

Despite the change in name, the G37 is still very much the coupe version of the latest G35 sedan. The higher number indicates its larger 3.7-liter engine and certainly hints at its more sporting intent. Along with adding the new engine, Infiniti brought the G37 up to date via a new body structure; the company says it's 36 percent stiffer than the previous generation's. The added stiffness combines with a slightly lower overall height, wider front and rear track widths, and revised suspension components for improved handling. This is especially true of models fitted with the available Sport Package.

Inside, the G37 benefits from the same transformation the G35 underwent last year. Materials are simply excellent, highlighted by such items as the car's new leather-accented magnesium transmission paddle shifters and the "Japanese Washi-paper finish" aluminum trim that provides a refreshingly unique take on cabin decoration. Additionally, a full array of standard and optional high-tech features will appeal to more technologically inclined buyers.

There aren't many entry-level luxury coupes on the market, but the available few are impressive. The new Audi A5 is worthy of cross-shopping with the G37, though it starts at a higher base price. The BMW 335i is a superior car, but it's more expensive than the G37 as well. The Infiniti's principal competition, therefore, is the BMW 328i, which is more involving to drive and a few steps ahead in interior materials quality, yet considerably less muscular under the hood than the broad-shouldered G. If you can live without the Bimmer's unmatched combination of sporty handling and a comfortable ride, then the 2008 Infiniti G37 should make an excellent addition to your garage -- as either a luxury coupe or a sports car.

The 2008 Infiniti G37 is essentially the coupe version of the G35 sedan. It's differentiated by unique styling, more power and two fewer doors. There are three trim levels available: base, Journey and Sport 6MT. The base model comes standard with 18-inch wheels, bi-xenon headlights, keyless ignition, leather upholstery, eight-way driver and four-way passenger power seats, a tilt-and-telescoping steering wheel, automatic climate control, a folding rear seat and a CD/MP3 player with satellite radio and an auxiliary audio jack. The Journey trim adds an eight-way power passenger seat, dual-zone automatic climate control and an in-dash six-CD changer.

The Sport 6MT trim refers to this coupe's six-speed manual transmission, and additional equipment includes a limited-slip rear differential, 19-inch wheels, high-performance tires, sport suspension and brakes, and sport-styled front seats with manual thigh extensions and driver's power-adjustable torso and thigh bolsters. Save for the manual transmission, these features are part of the Sport Package available on automatic-equipped G37s.

The Premium Package available on all G37s includes a sunroof (also available as a stand-alone option), a power steering wheel, driver memory, heated front seats, Bluetooth connectivity, an upgraded Bose stereo and an iPod interface. Available in conjunction with the Premium Package is a navigation system that includes real-time traffic information, voice activation, a rearview camera and a 9GB hard drive for music files. The Technology Package can be added when both aforementioned packages are selected; it includes adaptive cruise control, adaptive headlights and pre-crash seatbelts. The G37 can also be equipped with four-wheel active steering (4WAS).

The Infiniti G37 is powered by a 3.7-liter V6 good for 330 hp and 270 pound-feet of torque. The base and Journey trim levels come standard with a five-speed automatic transmission with paddle-shift automanual control, while the Sport 6MT features a six-speed manual. In performance testing, an automatic-equipped G37 Journey accelerated to 60 mph in 5.5 seconds, while a Sport 6MT coupe pulled a nearly identical 5.4 seconds to 60 mph. Infiniti estimates fuel economy at 18 mpg city/24 mpg highway for the automatic G37 and 17/26 for the manual model.

All 2008 Infiniti G37s come standard with stability control, traction control, front-seat side airbags, full-length curtain airbags and front-seat active head restraints. Models with the optional Technology Package get adaptive headlights and front seatbelts that can better prepare for front occupant safety if a collision is anticipated.

The 2008 Infiniti G37's stiff chassis reminds you that every moment you waste running errands in suburbia could be better spent on some remote back road utilizing the G's athletic moves. Yet, surprisingly, the tautly calibrated chassis (even with the sport suspension) proves compliant over most pavement surfaces, once again fueling the idea that the G coupe is as much a luxury car as it is a sport one. In other words, the G37 is ready for just about any driving occasion: daily commute, 800-mile road trip or blasting through that remote mountain road.

We'd stick with the standard steering setup, as the four-wheel system (4WAS) that varies the steering ratio and swivels the rear wheels up to 1 degree fails to weight up properly in the corners and provides limited feedback. We'd also probably stick with the standard five-speed automatic and its quick-shifting paddles mounted on the steering column, which blips the throttle for rev-matched downshifts. The Sport 6MT trim's manual transmission has a clutch that errs on the side of heavy and engages abruptly, while the shift lever is slow to move through its gates.

Forward of its cramped rear seat, the G37 coupe is practically identical to the G35. That means the sedan's user-friendly controls, excellent build quality and handsome design appear in the coupe as well. The available sport seats, with their adjustable bolsters, are very comfortable and snugly hold you in place -- perhaps a little too snugly in the posterior area. Unlike the sedan, though, the front seats are mounted slightly lower and offer a greater range of motion. This is good news for taller drivers, but others may find the resulting higher cowl results in a more confining environment. For good or bad, the G definitely "feels" more like a sports car despite the plush, luxury car surroundings.

As in many coupes, rear legroom is scant, and rear headroom is particularly compromised by the G37's severely raked back window. Plus, the trunk is on the small side, with only 7.4 cubic feet of space. The rear seats flip forward, though, to allow the transportation of bulkier items.