Reaction varied from snickers to scorn about Germany’s leading luxury car builder trying its hand at the American SUV market, but the idea worked so well that Mercedes is now after bigger game. Literally.

The Mercedes GL450 is large, at 200.3 inches long, 121.1 inches wheelbase, 76 inches wide, 75.6 inches tall, and 5,300 pounds heavy. It is powerful, with a new V8 churning out 335 horsepower and 339 foot-pounds of torque. It is high-tech, with the 4.6-liter engine’s 32-valve, dual-overhead-camshaft layout featuring variable valve-timing on both intake and exhaust valves and a 7-speed automatic transmission with fingertip manual controls.

It is strong enough to tow a 7,500-pound trailer. It is rigidly safe, with the world’s first unibody chassis on a full-size SUV, featuring 60 percent high-strength steel, and all the latest traction and stability control features, plus eight airbags surrounding all occupants, including side-curtain head protection for all three rows.

While the ML vehicles are stylishly attractive with their aerodynamic slopes and contours, they also are quite compact. Mercedes still makes the aging G-Class large SUV, and when it tried to eliminate the 27-year-old pre-Hummer squareish G, protests became so plentiful that the company decided to keep making it, for military and niche-sale use.

Between those extremes, Mercedes introduced an all-new R-Class a few months ago, and it is a unique people-hauling wagon that might best be described as an "on-road SUV."

So the GL jumps into the mix as something of a more rugged, more masculine, off-road-capable complement to the family on-road R-Class. In case anybody wonders why Mercedes seems to be intend on expanding its SUV presence, Mercedes officials point out that the GL, M, and R classes, and that those three vehicles will account for one-third of all Mercedes sales.

All three vehicles are being built in the expanded and adjacent two-plant facility in Vance, Alabama, located midway between Tuscaloosa and Birmingham. One plant will build the M and GL, and the other will build the M and R.

With a price yet to be determined, estimates run in the "high-$50,000" range, which puts the GL into my usual category: The best German vehicles are expensive, and, based on quality and technology, worth every penny.

When I first saw the GL at the Detroit Auto Show, and again at Chicago’s show, I was curious. It was clearly larger than the ML, as if some giant robot had stretched and enlarged an ML from every dimension. Still, it retains some stylish contours at the front and along the sides, but I wasn’t sure what Mercedes was aiming at with the vehicle.

After the chance to drive some early production vehicles on freeways and highways northward from San Francisco, and through the hilly wine country of Napa Valley, the GL creates and fills its considerable space.

The Mercedes GL was unveiled to the world’s motoring press this past week at a very interesting and very exclusive new resort in the heart of Napa Valley’s wine country, and while planning a late-winter gathering in California seems logical, this particular week included almost constant rain, which has drenched the countryside north of San Francisco with the kind of puddles and mud that only grapes can appreciate.

Still, what could be better for test-driving a new SUV – the first full-size SUV built by any European company? The big beast had impeccable road manners, and the seats are comfortable and supportive enough that I quickly adjusted from feeling that I was sitting too high to feeling comfortably in full control.

That was true on the freeways leaving San Francisco, and the two-lane highways selected to prove handling capabilities on the switchbacks in the mountain ranges flanking the Napa Valley. Having passed the normal-routine driving requirements with ease, the GL later proved its worth on some muddy stretches and off-road adventures as well.

"We didn’t want the just enter the full-size segment," said GL-Class manager Ron Mueller. "We wanted it to be the Mercedes of big SUVs."

After the presentation, someone asked what specific vehicles Mercedes was aiming the GL at, although it seemed an easy answer, because the only "full-size" SUVs in the industry are basically four vehicles -- the General Motors cluster of Suburban/Tahoe/Envoy/Escalade that are variations on one essential vehicle, the Ford Expedition, the biggest Lexus LX470/GX470, and the top Range Rover.

Mercedes officials, however, didn’t name any competitors, saying simply that any utility vehicle priced above $40,000 would be a competitor. They also said they don’t use any other company’s vehicles as benchmarks, because they have a specific, and quite rational plan. And they don’t expect to lose ML buyers, just offer them an alternative.

"We won’t take away ML buyers, but we will stop ML owners from going elsewhere for larger SUVs," said Geoff Day, director of Mercedes communication. "Our only benchmarks are internal – our customers’ expectations. The key is, after two kids, compact SUVs just are not big enough." In styling, the ML looks compact, the R looks long and slinky, and the plan for the GL was to look more rugged, to convey the sense of size and girth. It comes with 18-inch wheels, but 19 or 20 inchers are available. Along with superb suspension and handling characteristics for the driver, all seven occupants have a lot to like about the GL.

The three rows of seats not only seat seven, but they will seat seven adults in comfort. The second row is the key, because it will seat three, and has a 60/40 fold-down arrangement.

Hopping into the far back third row seats is easy, and the third row’s two seats are split 50-50, and, at the touch of a pair of side-wall-mounted switches, either the right or left, or both, seat cushions drop down just enough and the backrests fold down on top of them, leaving a flat, carpeted stowage floor. Mercedes claims "zero-to-flat" in 4.9 seconds.

Of course, the folded down area meets the folded-down second row to create a huge space, measured at 83 cubic feet.

The keys to comfort in the third row are that passengers have a roomy footwell, and a large skylight that is similar in size to the sunroof that opens for the front and middle passengers. Dual rear video screens, rear audio controls, and a 440-watt harmon-kardon audio system can be set to play iPod or MP3 or those old-fashioned CDs on separate controls, so rear-seat occupants can listen to something completely different from mom and dad up front.

Four-corner air-suspension facilitates adjustable ride height, which can be lowered three inches for serious off-roading, and which lowers itself a half-inch for optimum freeway aerodynamics.

While anyone seeking a vehicle in the over-$50,000 category will find the basic GL well-equipped, there are some upgrades available in the GL that set it apart. Options include the power rear liftgate, pushbutton-start keyless entry, rear videos imbedded in the backs of both front headrests, a rear-view back-up camera, full heated leather seats, and burled walnut trim.

The R-Class has the same platform but with stretched wheelbase, and while it has full-time 4Matic all-wheel-drive as well, it is not considered a "full-size SUV," which allows Mercedes to call the GL the only unibody full-size SUV.

Taking all the attributes of the R, the GL adds some rugged off-road features to assure capabilities beyond people-hauling. A two-speed transfer case, for example, with locking differential, adaptive damping, and higher ride-height adjustment from 3 to 4.5 inches.

Less than 2 percent are projected to choose the off-road package, which about mirrors the normal tendencies SUV owners have shown for serious off-road ventures. The R has fulfilled a lot of needs, but the GL takes most of the R’s assets and expands on them.

"We are looking at traditional families who still want and need a full-size SUV," said Mueller. "Our research shows that among all full-size SUV buyers, 30 to 35 percent own a Mercedes-Benz sedan."

So if ML owners need more room, they’ve always had to look elsewhere. Now they can look at the GL and stay within the Mercedes realm.

And if some Escalade, Expedition or LX470 buyers check out the GL, Mercedes probably won’t mind a bit.