• by Mark Walsh  @markfwal, March 18, 2011

Apple and Verizon Wireless have been tight-lipped so far about early sales of the Verizon iPhone, which launched Feb. 10. Speculation has been that it hasn't been flying off shelves. But in its latest monthly metrics report, Millennial Media offers some numbers on the new device as an ad vehicle.

The mobile ad network said the Verizon iPhone accounted for 4.5% of all U.S. impressions in the two weeks after it debuted, and has reached 5.8% in the first month (not including Wi-Fi). That's not too shabby after just a month.

Millennial did not provide data on how many Verizon iPhones are showing up on its network, but spokesperson Erin McKelvey said the device is delivering "an engaged audience based on the number of impressions we are seeing."

Among wireless operators, Verizon accounted for 20% of the network's impressions, second only to the 24% from Wi-Fi connections through multiple carriers.

When it comes to smartphone operating systems, Android was the top platform on Millennial's network for the third straight month. The Google OS in February accounted for 51% of impressions, down slightly from 54% in January. It still held a sizable lead over Apple's iOS, which had a 27% share, and BlackBerry-maker Research in Motion, with 17%. Impressions from smartphones overall are approaching the two-thirds mark, at 62% last month.

The connected device category jumped to 14% of impressions from 9% in January. With its latest report, Millennial started reporting the share of platforms being used on gadgets other than phones. No surprise: iOS accounted for 80% of impressions in the segment as a result of the iPad's dominance, with Android-based tablets making up most of the balance (17%).

The iPad 2 sold an estimated 500,000 units in its opening weekend this month, and eMarketer predicts that Apple will end up selling some 50 million tablets between 2010 and 2012. More than 32 million Android tablets are expected to be sold by 2012.

Looking at device makers, the biggest change since last month was a 50% share gain by Samsung to reclaim the No. 2 spot from HTC behind Apple. Handset models, including the Epic, Fascinate and Forte, drove Samsung's 23% portion of impressions.

The Samsung Galaxy tablet also cracked Millennial's top 30 devices last month. The iPhone remained by far the leading device -- accounting for 16.5% of impressions -- followed by the iPod, 9.1%, and the Samsung Epic, 7.8%.