Yahoo has had its “grown up” Valley CEO.

It has had its studio mogul CEO.

It has had its returning visionary founder CEO.

It has had its hard-charging, execution-centric CEO.

It has had its misrepresenting, train-wreck, patent troll CEO.

And now, with the stunning appointment of Marissa Mayer, Yahoo tries to go yet another route: A CEO with bona-fide Web tech chops. Give the new board credit for one thing: At least it’s not repeating mistakes of the past.

This announcement has sent the Valley into utter confusion and disbelief. It was a move that even Yahoo soothsayers AllThingsD couldn’t anticipate, and certainly one that has made interim CEO and fellow candidate Ross Levinsohn very unhappy.

The stunning part isn’t that Yahoo wanted Mayer. She has been one of the most hotly recruited Valley executives for years. It’s that Mayer actually said yes.

Even Jason Kilar of Hulu reportedly said no, and no offense to Kilar, but he’s no Marissa Mayer. She’s Sheryl Sandberg-like in her ability to be a polished spokeswoman and an effective take-no-bullshit executive, but she also has technical chops that aren’t always part of that package. And having seen her in action as a final judge at TechCrunch Disrupt for years, I can attest that she has an uncanny ability to know where technology is going, what is truly disruptive, and what will and will not resonate with consumers. (And she’s got some sweet dance moves, as we saw from the Ed Lee video last year… Sorry, Marissa. That gif is not going away.) She’s not just a dream candidate for Yahoo; she’s a dream candidate for nearly anyone.

Does her decision merely telegraph Mayer’s ambition, that after years helping guide several divisions at one of the most powerful technology companies in Valley history, she is not only ready to be a CEO but do a good job in a corner office that has made anyone who came close to it look incompetent? Or does Mayer know something we do not?

I haven’t talked to her, and won’t pretend to hazard a guess.

It’s easy to think of Mayer as a “new Tim Armstrong” — a successful, well-heralded Google exec. who may have looked good as part of Google, but could well struggle taking on an aging, dysfunctional Web giant. That playbook hasn’t worked well for Armstrong, and arguably Mayer is taking on an even more dysfunctional Web giant with Yahoo.

But Armstrong was a sales guy; Mayer is a technologist. The move seems to telegraph that Yahoo will be going back to its roots, focusing her design and product eye on strengths like mail, finance and sports, but I doubt that means she’s going the sheer news and media direction that Armstrong took AOL even with Yahoo’s strengths in these areas. And my guess is Mayer will put her connections and talents picking good upcoming startups to work with some acquisitions. I’m honestly not sure if that’s a good thing, but if I’m right, at least it’s a strategy.

Having closely watched Yahoo through most of these CEOs, it’s hard to be optimistic. I think an organization this beleaguered, this bloated, this siloed needs more than a great CEO. But I can say for the first time in the last three CEO hires, Yahoo may have its first real shot at regaining relevance in a long time.