The jury is in: Bob Lutz has had a huge, positive impact at General Motors.

Lutz, vice chairman-product development, was hired in 2001 to do one thing, shake the cobwebs off GM’s product development team and put some pizzazz back into its cars and trucks.

And almost from the beginning he has come under close scrutiny from the press, which maintained a healthy dose of skepticism about whether the man who led a 1990s product renaissance at Chrysler could work the same magic with the gray-flannel crowd at GM.

In his early 70s when he came aboard, it was unclear whether Lutz had enough left in the tank to whip into shape a bureaucracy as stubborn as GM’s, and it was questionable whether he still had his finger on the market’s pulse.

Some of the early signs weren’t encouraging. Although he garnered points for stripping plastic cladding off the ’04 Pontiac Grand Prix, media types blanched when Lutz called the car “the best performance sedan, certainly for a domestic, that I’ve ever driven.” The Pontiac GTO he championed, a solid performance sedan imported from Australia, was a styling yawner and a U.S. market flop.

GM insiders counseled patience, saying Lutz’s full impact wouldn’t be seen until 2006 or 2007, but critics were antsy for more empirical proof.

Since then the evidence has been mounting, mostly in Lutz’s favor. He is credited, for example, with leading GM’s effort to leverage its global vehicle platforms and designs, eliminating costly duplication of effort and giving birth to a promising cross-Atlantic linkup between Opel in Europe and Saturn in the U.S.

He also ripped the chains off GM’s design team. Just take a look at the creative difference between today’s Chevy Malibu and the ’08 model unveiled this month.

Although too early to call them hits, GM has quieted skeptics with the debut of revamped fullsize SUVs and new Saturn Outlook/GMC Acadia/Buick Enclave cross/utilities, redesigned ’08 Cadillac CTS sedan and upcoming Chevrolet Camaro coupe and convertible, all being ushered in under Lutz’s direction.

You had to sense Lutz was calling out his doubters at the Detroit show when he noted the Saturn Aura sedan and Chevrolet Silverado pickup had been selected car and truck of the year by North American auto writers.

“This is vindication,” he said, hitting that last word hard, “for the talented people at GM who want one thing and one thing only – to return GM to the top of the world in automotive excellence.”

Of course the summit has yet to be reached. Some of GM’s cars and trucks still trail competitors in quality, content and resale value, and the auto maker continues to spend more than many on incentives, a sign there’s ground to be gained by its myriad brands.

Plus, the biggest hurdle – maintaining the momentum post-Lutz – looms in the distance. Complete vindication will be won only if GM can make the Lutz formula a lasting component of its corporate DNA.

But for the moment at least, GM and its product czar have earned the right to say, “I told you so.”