James Martin/CNET

Sales of Microsoft's Surface may not set the tablet world on fire, but CEO Steve Ballmer still sees a key role for the device.

In an interview published today by MIT Technology Review, Ballmer snuck past the initial question of whether he was pleased with Surface sales.

"I'm super-glad we did Surface," Ballmer said in response. "I think it is important -- and not just for Microsoft but for the entire Windows ecosystem -- to see integrated hardware and software."

But the CEO did concede that Surface isn't likely to dominate the PC market.

"Surface is a real business," he told the publication. "In an environment in which there's 350 million PCs sold, I don't think Surface is going to dominate volume, but it's a real business."

The Surface RT tablet launched late October, while the Pro edition sales kicked in about a week and a half ago. But Microsoft has yet to share any hard sales numbers, leaving analysts to offer their forecasts.

IHS iSuppli analyst Rhoda Alexander told CNET late last month that initial shipments of Surface to retailers probably numbered around 1.25 million. But actual sales to customers "were significantly lower, maybe on the order of 55 to 60 percent of that figure," meaning somewhere between 680,000 and 750,000.

Alexander didn't see that percentage as unusual, citing the same results for certain new Android devices. But the return rates on the Surface RT tablet have been high due to a steep learning curve for Windows 8, she noted.

The analyst said at the time that she did expect more momentum across the industry for the Surface Pro model and similar devices. Surface RT runs Windows RT, which limits people almost exclusively to Windows Store apps. Surface Pro runs the full version of Windows 8, allowing people to install and run their traditional desktop applications.

Surface Pro did debut to a promising start. The tablet sold out fairly quickly during its initial launch, at least at Microsoft's online store. After stocking up on more inventory, the store now shows a wait time of 10 days for the 128GB edition. The 64GB version is immediately available. Other retailers, such as Best Buy and Staples, have also been working to increase their stock, according to Microsoft.

Beyond contributing its share of sales, Surface was also designed as an example for Windows PC and tablet vendors.

In the interview, Ballmer pointed to pen computing as something that Microsoft had touted for years. But the company apparently ran into resistance from manufacturers who weren't sold on the idea. Surface is an attempt to avoid that same mistake.

"Now we're trying to lead a little bit with Surface Pro," he said.