Speaking in Seoul, Korea, Microsoft CEO Steve Ballmer waxed ecstatic about Windows 8 and its importance to the company. Calling it the "dawning of the rebirth of Microsoft Windows," Ballmer said, adding that it was the "deepest, broadest and most impactful" version of Windows to date. Effusive praise of Windows products is obviously a common theme with Ballmer, but he also reportedly floated an estimate that 400 to 500 million users would "have" Windows 8 next year — presumably referring to a combination of upgrades and sales of both PC and WinRT tablets. Ballmer also estimated that 350 million devices running Windows 7 will ship by the end of 2012.

Big estimates from Microsoft should be no surprise, but it's worth noting that the slippery definitions between "have," "shipped" and "sold" could come into play as the company tallies up its metrics. Even with that variability, it's clear that Ballmer is expecting a big boost with Windows 8. Ballmer's claim that it is "the most important piece of work we've ever done" may be over the top, but it at least points to Microsoft's ambitions with the Windows 8 family of products: solidifying its PC dominance and finally gaining a real foothold in the tablet market.

Update: Microsoft reached out to clarify that Ballmer's 400 to 500 million number wasn't specifically an estimate of sales numbers, but a general example of the scale of the Windows in the marketplace and how that represents a significant market for developers.