Microsoft CEO Steve Ballmer says his new Surface Tablet sales "are starting modestly," he told French newspaper La Perisian. But not all signs point to flop. Ballmer claims this slow start has more to do with supply than demand (a refrain we're familiar with from the Apple camp). The company hasn't given any exact sales figures, but he's said those sales were constrained by few sales channels: Eager Surface owners can only get the tablet from the Microsoft Online Store, or at certain physical retail stores in the Canada and the U.S. Ballmer makes it sounds like there just aren't enough Surfaces to go around, which tracks with the "out of stock" message that the online store posted on November 1, one week after launch.

Making things more complicated, though, is that as of now, none of the models appear to be backordered on the website. Plus, as we learned from the iPad Mini, "selling out" can mean a few combinations of high demand and low supply, not necessarily killer sales for the tablet. And if the tablet were doing really, really well, we'd expect Ballmer to give a more enthusiastic take on its sales figures, as Amazon's Jeff Bezos has done with the Kindle Fire

In any case, Ballmer expects sales will pick up once Microsoft releases the higher-end version of the Surface, the Surface Pro, which can run the full version of Windows and might appeal to people who want to use the tablet as a lightweight computer. Many reviewers have complained about the current model's Microsoft RT operating system, which is a stripped-down version of the full Windows 8. The Pro, which comes with the full Windows 8, comes out in January 2013. Then maybe Ballmer will sound more assured of the Surface's progress, and maybe he'll even give us some sales numbers.