Consumers take advertising slogans with a grain of salt, and rightfully so. That's what makes it so hard to believe BMW's tagline, "The Ultimate Driving Machine." But BMWs really are fantastic driving machines, and the Z4 is the ultimate expression of BMW's ultimate goal.

BMW replaced the Z3 with the Z4 in 2003, initially offering only a two-seat roadster body style. The hard-edged styling was controversial at the time, but over the years consumers have come to accept it. The styling was mildly updated in 2006, when BMW introduced new engine choices, a sensuous hatchback coupe, and a high-performance M model. The Z4 carried over virtually unchanged for 2007.

With only two seats, rear-wheel drive, and a base price in excess of $36K, the 2007 BMW Z4 isn't a practical family car. It's better thought of as a second car. But, oh, what a second car it is.