Microsoft is holding its Windows 8 launch event right now in New York City, where Windows chief Steven Sinofsky is on stage talking up the new operating system prior to its debut in stores tomorrow.

He started with a defense of the massive overhaul of Microsoft’s flagship product, pointing out that the traditional Windows interface was made for a different era before pervasive connectivity and devices.

“We shunned the incremental,” said Sinofsky, calling Windows 8 the best version ever made. “We boldly reimagined Windows.

He noted that Windows 8 has been through 1.24 billion hours of testing.

For anyone wary of the new Windows 8 experience, Sinofsky noted that the “heart of the Windows 7 desktop still remains” available to Windows 8 users.  Every new Windows 8 PC will come with a simple “how-to” the first time you launch a machine.

Addressing the new Windows Store app market, he said, “We know that some might rush to count apps and look for their favorite apps in the store. We see today as a grand opening and a very solid one.” He said it’s launching with thousands of apps, more apps than any comparable app store at their launch.

Discussing Windows RT, the version for machines running ARM processors (including Microsoft Surface), Sinofsky highlighted the compatibility with peripherals, including top-selling printers.

Update: After a demo of new Windows 8 tablets and computers, Microsoft CEO Steve Ballmer comes on stage, says Windows 8 “shatters perceptions” of what a PC is. “Windows 8 PCs are the best PCs ever,” he says, calling the lineup “diverse and stunning.”

The event is ongoing, viewable via the Microsoft webcast embedded above.

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