Analyst Jack Gold of J. Gold Associates estimated that, assuming 20% of the 1.5 million are still in carrier sales pipelines, consumers owned approximately 1.2 million WP7 smartphones.

Handset makers began selling WP7 smartphones to European customers in October, and to U.S. consumers in .

"At launch, Windows Phone 7 was underperforming," said Ramon Llamas, an analyst with IDC, referring to the paucity of product when AT&T and T-Mobile launched WP7 devices last month in the U.S. "But the marketing push since then has been pretty solid."

"I don't think that those sales are bad, but they're not in the same category as an Android or iPhone launch," said Gold, "although Microsoft is certainly doing much better than they did with the Kin." He was referring to the phone last summer after dismal sales.

Llamas, however, declined to characterized the 1.5 million milestone as either strong or weak.