Windows Phone 7 has a meager 1.3 percent of the U.S. smartphone manufacturer share, Nielsen says. That's less than half the 3 percent share of Windows Mobile Phone -- the OS that Windows Phone replaced.

In terms of hardware sales, Apple has a commanding lead. More than a third (34.3 percent) of smartphone owners use an iPhone. Samsung is a distant second with 17 percent, followed by HTC (14 percent) and Motorola (11 percent).

As expected, consumers are steadily replacing their older cell phones with smartphones. In fact, two-thirds of new mobile buyers chose a smartphone, Nielsen reports.

Contact Jeff Bertolucci at , Twitter ) or and follow on Twitter, too.