In a survey of "recent acquirers" of smartphones, market research firm Nielsen Mobile finds that Google, Inc. (GOOG) continues to eat everyone's lunch -- particularly Waterloo, Ontario-based Research In Motion, Ltd. (TSE:RIM) and Redmond, Washington-based Microsoft Corp. (MSFT).

In July, Nielsen placed the market share of Google's Android OS in the U.S. at 38 percent.  Three months later, for the period ending in August, Nielsen finds that Android has risen to 43 percent of all active U.S. smart phones, a gain of five points.  More importantly, among those who bought their phones in June, July, or August, Google had a formidable 56 percent market share.

Don Kellogg, Nielsen Director of Telecom Research & Insights, says this recent adopter figure is particularly important.  He comments [press release], "The preferences of these so-called "recent acquirers" are important as they are often a leading indicator of where the market is going."

If correct, the market appears to be going towards Google and away from RIM and Microsoft.  Overall RIM is clinging to an 18 percent market share while others (mostly Microsoft) hold a remaining 11 percent.  However, in the last three months only 9 percent of buyers chose BlackBerry handsets (RIM) and only 6 percent chose "other" (a Windows Phone) handset.

Apple, Inc. (AAPL) held steady -- it had a 28 percent market share at present, and in the last three months precisely 28 percent of buyers, according to Nielsen, bought iPhones.  In other words Microsoft and RIM are either stagnate or slightly shrinking in unit sales, Apple is growing unit sales at the same rate as the overall growth of the smart phone market, while Google is growing faster than the overall market.

Nielsen cautions that Apple's apparent stagnation is likely more a side effect of lacking new hardware.  Writes Mr. Kellogg, "Every time Apple launches a new iPhone or makes it available on a new wireless carrier, there is an increase in their sales."

Apple is expected to drop its fifth generation iPhone model at a special event next Tuesday.

The study also reveals smart phone uptake continuing to rise.  Overall at the end of August, only 43 percent of U.S. phone customers had a smartphone.  In the last three months, though, smartphone purchases have risen to 56 percent of total purchases, as sales of feature phones continue to shrink.