Microsoft has finally opted to release some sales figures for Windows Phone 7, the company’s in-house iPhone killer. In the first six weeks since the operating system hit the market, 1.5 million handsets have been sold, a number the company says is “in line” with expectations. “We know we have tough competition, and this is a completely new product,” Microsoft VP Acim Berg said in an announcement. “We’re in the race-it’s not a sprint but we are certainly gaining momentum and we’re in it for the long run.”Microsoft’s mobile marketshare has dipped significantly in recent year, thanks to the presence of Apple’s iPhone ands Google’s open Android OS. It’s hard to compare, um, apples to apples here, but as a point of reference, the latest version of the iPhone sold one million units in its first three days.But while a number of different manufacturers released phones running the OS, many of the initial Windows Phone 7 handsets were plagued by shortages.