What Is It? A convertible grand tourer with power to spare and a host of electronic gadgets.

Powered by: A 5.0-liter V-10, producing 500 horsepower and 383 pound-feet of torque.

Cost: $104,900. As tested with options, including destination and gas guzzler tax, $114,990.

Competitors: Mercedes-Benz SL55 AMG, $128,800. Jaguar XKR, $92,500.

Not surprisingly, BMW's marketing for the M6 convertible ??“ one of the luxury manufacturer's most expensive models ??“ places the emphasis on gratification, coaxing drivers to simply "indulge."

It's a telling tagline. BMW's M division produces high-performance editions of the company's vehicles, many of which have, over the years, become legendary with BMW diehards for their race-car handling and power.

But, the M6 strays from that formula. As fast as it may be ??“ BMW clocks its zero to 60 miles per hour time at 4.6 seconds, the M6 isn't like other M-badged vehicles -- and isn't necessarily the purist's choice because it's a big, heavy convertible. Soft roofs compromise underlying structural rigidity while the mechanisms to raise and lower them add performance-inhibiting weight.

The M5 sedan, which shares the M6's 500 horsepower V-10 engine, hews more closely to the traditional M-vehicle pattern.

All of which, brings us to the question: superlative power notwithstanding, is the M6 convertible really worthy of the M badge? The answer lies somewhere between yes and no.

BMW purists have begun to question whether M cars are losing their edge as the company tries to expand sales by appealing to a wider constituency of customers.

But, a few moments behind the wheel of a M6 convertible suffice to make the debate seem largely irrelevant. The car's performance puts it in league with higher-end brands like Aston Martin and Ferrari.

Unlike some competitors that hang on to electronic control even when traction systems have been deactivated, the M6 can be divorced from its safety nanny. The steering is linear, perfectly weighted at any speed, and full of feedback.

The M6 is also a technological bomb shell that can be tailored to the driver's preferences. The engine electronics have three settings, the SMG transmission provides 11 different shifting programs and the electronic suspension can be tuned to three levels of shock-absorber firmness.

The roar of the engine permeates the cabin, top up or down, adding further sportiness to this grand tourer. Less exhilarating is the deafening roar of the wind with the top down. A glass rear window can be raised to help mitigate the noise.

For 2008, the BMW 6 Series and the M6 are receiving some modest upgrades as part of a midcycle refresh, though the elegant exterior will remain. A host of new interior goodies will be available from different colors to new chrome trims. Most of these options, at least for the M version of the vehicle, are cosmetic.

Whether the M6 is truly worthy of its M badge is likely to continue being a topic of heated debate among the BMW faithful. Regardless, for its looks, price, and power, the M6 convertible could easily stand in as the company's flagship vehicle.

Write to Matt Vella at matt.vella@wsj.com

Source: [url=http://online.wsj.com/article/SB118434133070165982.html?mod=googlenews_wsj]Wall Street Journal[/url]