The 2007 Infiniti M series is enough to give German automotive engineers insomnia. The M35 and its more powerful sibling, the M45, demonstrate that Japanese luxury brands are steadily learning from their mistakes, improving their product and posing an increasing challenge to the traditional luxury cars from Europe.

The Infiniti M successfully blends aggression and sophistication for stylish visual flair. Its rosewood-trimmed interior is luxurious, with comfortable seats and a full array of standard safety equipment. Every model features the requisite luxury accoutrements, including keyless push-button starting.

The M35 can be rewarding to drive. Its V6 engine is one of the most powerful available. Enthusiast drivers will particularly like the M35 Sport, which features a firmer suspension and active rear steering. The V8-powered M45 delivers even stronger acceleration; the M45 is also available as a Sport model.

Those who live in slushy, snowy climates should be wary of the Sport versions of either M, however. These cars are equipped with sticky speed-rated tires, which are designed for lots of grip on dry pavement, and aren't much good for anything in snow. Better to choose the all-wheel-drive Infiniti M35X, which comes with general-purpose, all-season tires. The M35X adds an element of confidence and security in sloppy climates, without a significant toll in fuel economy.

Sedans in the $50,000 range comprise one of the most competitive chunks of the new car market, loaded with good cars like the Audi A6, BMW 5 Series, Cadillac STS, Jaguar S-Type, Mercedes-Benz E-Class, Lexus GS, and Acura RL. The Infiniti M leans toward the sportier end of this spectrum, particularly in Sport trim. We strongly recommend a look at the Infiniti M35 or M45 for anyone looking for a car in this class.