Millennial Media is out with its quarterly device barometer: Mobile Mix. The report tracks the top devices and operating system share on its network. It's based on a different methodology (share of ad impressions) vs. Nielsen or comScore, which both rely on surveys.

It's not a totally "objective" view of the marketplace. But its helpful to identify and monitor trends on a directional basis. The three big trends identified in the document are the following:

• Increasing percentage of smartphones on Millennial's network (now 74%) vs. 50%+ for the overall mobile market
• iOS growth and slight Windows Phone growth vs. other operating systems. It appears the iPhone grew at Android's expense, while Windows grew at RIM and "other's" expense
• The document also shows the growth of "connected devices" (tablets)

Here are the charts that illustrate the above: 

In the future the tablet market will be a contest between Apple, Google and Amazon. Samsung, unless it decides to price things much more aggressively, will be marginalized -- at least in the US.