Microsoft's 2012 Build conference for Windows developers kicked off in Redmond yesterday, and CEO Steve Ballmer was on hand to deliver the day one keynote.

Naturally, he took the opportunity to talk about the launch of Microsoft's new product range – and Windows 8 in particular – with his trademark enthusiasm.

"Windows 8, Windows Phone 8 and Microsoft Surface are all now really here," he explained, before asking himself, "how are they doing?"

Well, Steve?

"In just the last three days, we have sold more than 4 million Windows 8 upgrades," Ballmer revealed.

He repeated for emphasis: "4 million Windows 8 upgrades."

According to Ballmer, those 4 million are "all individual users buying a copy or stores stocking shelves for what they see is the demand.

"We have sold, additionally, tens of millions of units to our corporate customers, who can upgrade when they want to."

Importantly, such figures mean Windows 8 has got off to a better start than its predecessor.

Mobile matters

That's good news for Microsoft, of course, but it's also good news for developers operating within the Windows Store ecosystem.

The platform's app marketplace remains relatively uncrowded, and has just been exposed to a massive influx of new users.

Ballmer didn't reveal any specific sales figures for the Microsoft Surface tablet, which launched alongside Windows 8 on 26 October, although he claimed that the level of interest in both products has been "stunning."



[source: Microsoft Build keynote]