Dag Kittlaus was speaking at a Crain’s Tech Talk Q&A session in Chicago Monday night. “I completely disagree with people who say it doesn’t work very well,” he told moderator Tom Ryan, CEO of hip t-shirt maker Threadless. “You don’t launch a product that isn’t into the 90th percentile of working if you’re using it properly.”

Kittlaus doesn’t deny that Siri has her issues. What Apple (AAPL) touted as the marquee feature of the new iPhone 4S last October, has let many users down. Common complaints have included slow responses and poor speech recognition. Apple launched Siri with a rare Beta label, a tacit admission of work in progress. What’s more, one former Apple insider recently told Fortune, that company employees “are embarrassed by Siri. Steve would have lost his mind over Siri.”

Naturally, Kittlaus pushed back during his talk. “You run into some connectivity issues occasionally,” Kittlaus told Ryan. “And of course, there are definitely moments where it takes a little bit too long, but it’s a very complex problem that they’re working very hard at fixing and making it perfect, and I think you’ll see it get better and better over time.”

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Kittlaus says “they’re” instead of “we’re” because he no longer works for Apple. In 2007, the former Motorola (MMI) executive helped launch the startup that gave birth to Siri. In April 2010, Apple bought the firm for an estimated $200 million. Kittlaus moved to company headquarters in Cupertino but quit about a year and a half later, around the time Siri was integrated into the iPhone 4S. After four years of nonstop development, he moved back to the Chicago suburbs where he grew up to spend more time with his family, work on a science fiction novel and cook up more ideas. He noted that his split with Apple was amicable.

But to Siri bashers, he’s not as cordial. Ryan read a comment sent to Crain’s by a user who said he enjoyed Siri — when it worked. “Sometimes it gets it right,” he read. “Sometimes it flat-out misses.” Kittlaus bristled and answered, “It’s not perfect,” which prompted Ryan to joke, “Don’t shoot the messenger. I’m just reading these questions.”

It may be hard to blame Siri’s inventor for taking criticism personally. Kittlaus is half Norwegian and says that Siri means “beautiful woman who leads you to victory” in his Nordic tongue. In fact, he wanted to name his first daughter Siri but a son came first.

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Kittlaus made his Siri defense just hours after the kickoff of Apple’s annual World Wide Developer Conference in San Francisco, the first helmed by CEO Tim Cook since Steve Jobs died. Along with refreshes to the MacBook line, a reveal of Apple’s next-generation Mountain Lion OS, and a newly designed Maps app, Apple revealed a number of key Siri upgrades that could alleviate some of the complaints — at least those over its lack of functionality.

New features accompanying a revamped iOS 6 this fall will include iPad availability, sports data, Yelp (YELP) reviews and OpenTable (OPEN) reservations. Siri will also be able to launch apps and post to Twitter and Facebook (FB). One of its most significant new features is “Eyes Free,” a car-integration system. According to Apple, automakers are planning to add a Siri button to steering wheels in the next year.

Kittlaus told Fortune he is most impressed with the sports scores because he said it was such a hot domain. “If you want Indiana scores, NBA, college basketball, Big Ten — it just eliminates a lot of clicks. It’s at its most powerful when it eliminates the work that you otherwise would have to do to get to that information.” He also noted the new Eyes Free feature. ” I wasn’t expecting to see car manufacturers putting Siri buttons in the car. I think that’s really exciting. And it’s safe.”

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When asked how close Apple’s latest round of upgrades has come to meeting his original vision for Siri, Kittlaus said, “They’re just getting going, and I can’t wait to see where they take it. They’re in a position to have this be one of the biggest things in the world in terms of a paradigm. They’re going after it, and I’m really excited to see where it goes.”

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