The M Roadster shares its distinctive, shark-like front portion and polarizing "flame surfacing" with BMW's standard Z4 models. The M version's wider stance and copious rubber, however, serve to de-emphasize all those flaming surfaces. Such mo-sports muscularity resolves the model's inherent design tensions in the same way The Hulk's green skin and purple clamdiggers added another dimension to Bruce Banner's denim-shirt-intensive wardrobe.

The thickly padded steering wheel, seemingly designed by tort lawyers, is awkward on first grab. After getting used to it, though, it becomes like a second appendage — think love handles. Interior upholstery is tastefully spartan, though BMW uses lots of a strange leather-like material across the dash that stains easily (keep the powdered doughnuts outside, please), and another type that's patterned to look like carbon fiber surrounding the binnacle and console. The leather seats offer more support than a jealous sugarmomma.

Zero to sixty in 4.8 seconds is plenty quick for any roadway application. The fifth star's withheld for odd catch points in first and second gears that sometimes harshed our mellow. Engaging sport mode is like pouring a pot of espresso into the intake; everything sharpens up, particularly when paired with a heavier right foot.

Ventilated, cross-drilled discs — lifted from the M3 — are epic. Word from other press testers who've done track work in the roadster is that they fade after a few hot laps. We didn't push hard enough to make it happen. Pedal feel is on the urgent side. (Side note: the system has a feature that keeps pads grippy in bad weather by bringing them close to the discs at times to dry the rain.)

Seating position is so low-down, getting into my knee-high Toyota MR2 Spyder afterward felt like climbing up to the bridge of the USS Nimitz. Ride is on the soft side of firm — making it a fine daily commuter — and not at all crashy over tough stuff. At times, I felt a slight numbness from the gas shocks that masked road feedback.

The M Roadster eschews the Z4's Servotronic vehicle-speed-sensitive power steering in favor of a good 'ol hydraulic power-assist system. It's proof the simplest option is often the most sporting, even with every technical advancement at hand. Handling is quick without being darty, and we didn't even get near adhesion limits. It's a freaking party on wheels.

Deciding not to offer the dual-clutch SMG box on the M Roadster may have been a technical decision, but doing so focused the roadster's purity of purpose. The ZF six-speed is smooth and willing, with ratios that appear to match the 3.2-liter six's power band as closely as can be accomplished without a mess of algorithms.

The test car had the premium package, which comes with BMW's bell-like premium sound system. The powerful deck can even overpower the sometimes harsh-n-raspy engine note, which can sound a bit untoward in the upper range.

It's hard to think in terms of economy considering a purely sensual, emotional purchase, other than that — pricewise — the M Roadster is cheaper than the Porsche Boxster S (which has its own charms) and the Mercedes SLK55 AMG, which has a V8 and is 0.5 second quicker. Nonetheless, the M kit boosts the price of a base Z4 by an accountant-busting $10,000.

Like the M3, the M Roadster has a neat set of lights on the tach that suggest safe engine speed based on oil temperature. An extra star added for BMW's leaving off iDrive, which would have been grossly miscast in the sport-spartan cockpit. The real toy is itself.

Two small weekend bags or a half-set of ladies golf clubs, your choice.

The M Roadster is more than the sum of its parts. It's got one of the best-considered balance of compromises and performance of nearly any roadster in its narrow class. Still, a considerable portion of its fun quotient can be had at a 50% discount in the Honda S2000, making it an indulgence that proves that the last 20% of a car's development can eat up half of its cost.

[by Mike Spinelli]

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