Google's Android platform is now the most popular operating system among people who bought a smartphone in the past six months, Nielsen reportedTuesday. It's yet another sign that Android is shaking up the mobile marketplace, but what does it really mean for Apple and for smartphone buyers?

Among recent buyers, Android held 32% of the market, while Apple and BlackBerry maker Research In Motion were in "a statistical dead heat" for second place with about 25%, according to Nielsen. The data include the release of the iPhone...