The first clue that the 2006 BMW M5 is no ordinary sedan comes at start up. The V-10 gurgles and gently shakes like a 1950 International Harvester, ominously heralding its tremendous power and latent energy. Yet, we were able to fit three baby seats on the beast’s back bench and then the sedan’s docile ride promptly put all the kids to sleep. It’s this split personality that makes the M5 so special. It can be a fierce, road-eating dragon and also a luxurious tourer.

As tempting as free doughnuts in the break room, the “M” button on the M5’s steering wheel is an indulgence too tempting to pass up. Press it and a tremendous surge of acceleration makes it feel as though you might actually become part of the car, producing greater pleasure than 1,000 Krispy Kremes. The car thunders forward, like pushing the “M” button somehow seriously pissed it off. We actually got goose bumps the first few times we tried it. You know how the hair will raise on the back of your neck when you hear a great song? That’s the feeling you get driving the 2006 BMW M5.

The SMG transmission takes getting used to. If you leave the car in default mode, the car limits itself to 400 hp and makes gear changes to maximize fuel efficiency. Up and down shifts are so slow, that, at first, we thought we were doing something wrong. We felt like teenagers again, behind the wheel for the first time and shifting badly, very badly with long pauses between gear changes and turtle-like takeoffs. But, once we fiddled with MDrive and set our own drive parameters, we became instant Marios, blazing through gears with superhuman speed and smoothness. The system even blips the throttle on downshifts so anyone outside the car thinks you’re the heel-and-toe champion of the world. And, best of all, we were able to make the switch between pimply teenager and smokin’ hot stud just by pushing that sinister “M” button on the steering wheel. If only there was an “M” button for everything in life.

Another of the 2006 BMW M5’s superb engineering tricks is how DSC allows the car to feel just a little unhinged during hard driving, as though you’re hovering right on the edge of adhesion and you need to work to control it. But it’s just an illusion because the car stays amazingly planted even when you’ve crossed the line. We know (and we’ve warned you about this) because we switched the system off and tried the identical maneuvers that thrilled us with DSC on and promptly went fishtailing all over the road, spitting gravel onto the shoulders like an M16. That was real danger, whereas with DSC engaged the BMW merely created the feeling of danger, right down to a puckering sensation below. Of course, no engineering, regardless of its brilliance can overcome the laws of physics, but within limits, the new M5 makes it feel pretty close.

You can also choose, via the Electronic Damping Control (EDC) button, between a soft ride and a super stiff one. The cushy ride, “Comfort,” is for cruising down a straight, smooth highway. The rigid ride, “Sport,” is for thrashing a twisty road to within an inch of its life. There’s also a “Normal” setting that offers a pretty good compromise between the two. We usually drove the M5 with the suspension set to Normal, and liked its balancing act between suppleness and firmness. But we really liked how EDC automatically tightened the shocks for more control and greater feedback when we decided to go hard into a corner, like the car was reading our minds. For a while, we fooled around, driving sedately one minute and then blasting into a curve the next – the M5 responded appropriately without fail.

EDC enhances a beefed-up version of the regular 5 Series model’s all-aluminum suspension system. For use in the M5, BMW added stiffer bushings, borrowed the rear links from the superb Z8, and added specially calibrated springs and shocks for maximum performance. Add to that the car’s well balanced 52.2/47.8 front/rear weight distribution and it’s no wonder we were thrilled each time we drove the M5. Despite the amount of technology that actually separated us from the road, it was as though were a part of the car, and extension of the hardware that thrummed along the highway.

Normally, the kind of performance demonstrated by the BMW M5 requires some compromise in terms of comfort, but this car asks nothing of you in return. Its big sport seats (with 16 adjustments for the driver and 14 for the passenger) and the spaciousness of the cabin make for one of the most comfortable rides around. Additionally, we never felt unsafe. During one controlled “M”-button-inspired burst, a cell-phone-yakking lady in a white Hyundai Santa Fe pulled out into the passing lane while she was doing 50 mph. We had just pushed the little better-than-doughnuts button and were planning on overtaking the cars in front of her. It was literally a life-threatening moment. We figured a nasty slide was our best outcome. But, thanks to the Bimmer’s megabrakes, we brought the car quickly to heel without drama. We didn’t even have to stomp on them and, afterward, we felt composed enough to honk at the offending driver, who had no idea how close a call it had been.