Last year, Microsoft held just over 10% of the market. But that was Windows Mobile 6.5, the final iteration of the Windows Mobile line. Version 6.5 was little more than window dressing with a capacitive screen thrown on for good measure to help people with swiping gestures. Windows Phone 7, written from the ground up to compete head to head with modern phone platforms, was launched in October internationally and November domestically. It has been slowly catching on, hampered by network availability. CDMA phones weren't ready until the spring of 2011, which locked it out of at least half of the North American market.
InfoWorld has obtained data from ComScore that points to a turnaround. Since May of 2011, Microsoft's share has been virtually flat, holding at just over the 5% level. You cannot tell from this data which devices are selling, Windows Mobile or Windows Phone, but given very few carriers still have Windows Mobile inventory, this flat spot indicates that as Windows Mobile surely continues to fall, Windows Phone is on the uptick.
There are also two significant factors that this data doesn't take into account. First is the Mango release, which is rolling out worldwide right now. Features like third party multitasking, group texting, and HTML5 support bring Windows Phone on par with Android and iOS in many areas, and certainly most of the important ones. The second factor is Nokia. The first Nokia device has yet to hit the streets. Nokia is readying its ad campaign for the Nokia 800, which many of us know as Sea Ray.
We'll have to wait for a few months to see whether both Nokia and Mango can change overall phone market trends, but I'd say Microsoft can finally breathe a sigh of relief that at least it is no longer losing share.