It’s official. Apple is the world’s most valuable technology company. On Wednesday, its market capitalisation surpassed Microsoft’s for the first time, clearly demonstrating the sea change that has occurred in the technology industry in the past 10 years.

The share price of Microsoft, under CEO Steve Ballmer, has spent the past decade floundering.

Of course, that doesn’t take into account the fact that Microsoft has returned billions of dollars of wealth to investors through dividends and share buybacks.

But Apple stock has leapt from one record high to another on a string of successful products — first the iMac, then the iPod, the iTunes Store, the iPhone and, most recently, the iPad.

The turnaround in Apple’s fortunes under CEO Steve Jobs, who returned to the company in 1997 — when it was facing the very real prospect of bankruptcy — has been nothing short of spectacular.

Over 10 years, Apple’s share price has risen 502%; Microsoft’s, on the other hand, has fallen 4%.

But it’s Microsoft’s weak performance in the past six months that may surprise industry watchers. In that time, the software maker’s share price has slipped 16% while Apple has risen by nearly 20%.

The euphoria around Apple is understandable: its financial results have continued to beat market expectations and the iPad, which has already sold more than 1m units — outpacing early sales of the iPhone — looks on track to repeat the success of other Apple products.

But Microsoft hasn’t been without a recent string of successes, too: its Windows 7 operating system has been warmly received by businesses and retail consumers, with reviewers giving it two thumbs up. Unlike Vista, which was plagued by driver incompatibilities and other issues, Windows 7 is a solid and stable product.

And the company’s new server and developer tools have also been given good reviews. Then there’s its upcoming Windows Phone 7 Series, which, based on demonstrations, should propel it back into the smartphone market when it’s released later this year.

Sure, it’s floundering in Web search, where it looks like a deer caught in Google’s headlights, but it has strong product lines that should continue to perform well for years to come.

Though market value doesn’t give a true reflection of a company’s size — rather it’s in large part a measure of the market’s expectation of future growth — the significance of Apple overtaking Microsoft is still difficult to overstate.

Apple, under Jobs, is the new king of the hill. The only question now is: how long will it stay there? — Duncan McLeod, TechCentral