It was pretty hard to get much of an early read on BMW's newest -- and most controversial -- M model, the 2010 BMW X6 M (the X5 M, which is being launched simultaneously, was unavailable for testing). Our initial short stint featured a bit of highway driving and a quick run on some slightly twisty roads, allowing us briefly to feel how smooth, yet powerful this 5300-plus-pound beast really is. You're in touch with the road, but there's no bounce or jounce in the X6 M, just smooth sailing -- even in the more aggressive M mode.

BMW had some real driving fun in store for us at our final destination -- several hot laps on the 2.54 mile, 12-turn Road Atlanta circuit. After a few lead-follow instructional passes, we were set loose in the X6 M on the famed racetrack. The massive elevation changes, fast sweepers, and blind, off-camber corners really show you what the X6 M is made of.

Exiting the pits, you stay right, wait for the first slight left-hander, then dive into a hard right that leads you into the esses. A fast, sweeping-downhill left leads into a fast, sweeping-downhill right, where you hit the apex and let the 547-horse, 501 pound-foot, twin-turbocharged, 4.4-liter V-8-powered truck drift out to the left edge. Then it's back up hill through the rest of the esses, which you can basically take straight.

Stay right to set up for the uphill blind left, then its back down to another fast right, and into the tightest corner, an almost 90-degree right that leads you onto the long back stretch. Here you'll nudge 140 mph (the X6 M is limited to 155 mph) before jumping on the binders in a downhill braking zone, then a quick left-right and head back to the pits.

We couldn't run full laps, but that ended up being a good thing. More on that later.

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