As part of a year-end release of data Nielsen indicated that 56% US mobile subscribers owned smartphones as of Q3. By contrast, comScore says smartphone penetration currently stands at 52%. And Pew said earlier this year that it was 53%.
In the smartphone segment, the following are Nielsen's data regarding US mobile operating system share (again, end of Q3):
Here are similar data from comScore's for comparison purposes (November, 2012):
Below are Nielsen's lists of top apps for 2012 for both the iPhone and Android devices. While the lists are different there are several apps that appear on both: Faceobook, YouTube, Pandora, Twitter and "weather."
Google's Gmail and search apps are at the top of the Android list but absent from the iPhone list.
Nielsen is also reporting that there are an average of 32 million Maps users on the iPhone each month. That's more usage than Facebook or YouTube, which both have huge mobile audiences in the US.
It's also a significant loss of traffic for Google. However because there were very few ads on the iOS 5 version of Maps it's not a revenue loss for Google.