A survey conducted by the Nielsen's of U.S. mobile consumers from July-September 2010 reports that the consumers planning on getting a new smartphone had a very clear preference: "33% wanted an Apple iPhone. Slightly more than a quarter (26%) said they desired a device with the Google Android operating system, and 13% said they wanted a RIM Blackberry."
According to Nielsen those same surveys for January 2011 -- March 2011 now shows that "31% consumers who plan to get a new smartphone indicated Android was now their preferred OS. Apple's iOS has slipped slightly in popularity to 30% and RIM Blackberry is down to 11%." Almost 20% of consumers are unsure of what to choose next.
Nielsen further reports that "as of March 2011, 37% of mobile consumers who owned a smartphone had a device with an Android OS. Apple's iOS, claimed by 27% of consumers, is now outpacing Blackberry, which has 22% of the market."