Despite reports of a slow start, Microsoft said on Tuesday that it has sold more than 1.5 million Windows Phone 7 devices in the first six weeks, but it's important to note that the number reflects the number of units sold to mobile operators and retailers and not necessarily direct to consumers.

When asked if the sales numbers met company expectations, Achim Berg, vice president of business and marketing for Windows Phone, said that "sales are ramping well" and that the numbers are "in line" with company expectations.

He said that to juxtapose these numbers with the competition would be a bit of an apples-and-oranges comparison, but added that Windows Phone 7's performance is in line with those of other first-generation platforms.

"We introduced a new platform with Windows Phone 7, and when you do that it takes time to educate partners and consumers on what you're delivering, and drive awareness and interest in your new offering. We're comfortable with where we are, and we are here for the long run' Windows Phone 7 is just the beginning," Berg said.

Berg acknowledged that the competition in the smartphone market is intense but for Microsoft, measuring success is more about the long term and not the short term. Microsoft plans to release the first of several updates in the coming months and will also add additional carrier partners around the world in 2011, including Sprint and Verizon here in the States, in addition to introducing a broader portfolio of devices at various price points.

Microsoft released its first Windows Phone 7 devices on October 21 in Europe and Asia, with the U.S. following closely behind on November 8. Currently, there are four smartphones available in the U.S.--the HTC Surround and Samsung Focus with AT&T, and the HTC HD7 and Dell Venue Pro with T-Mobile--and at least half a dozen other models in other parts of the world.