The report, which surveyed more than 4,200 people, found that 21% of US wireless subscribers had a smartphone by the end of 2009, up from just 14% a year ago.
Of all phone users, 14% had downloaded a mobile app within the last month. However, smartphone users were consuming far more apps, reporting on average 22 apps on their devices compared to just 10 on feature phones.
Users with iPhone reported an average of 37 apps, as many as the average number of apps on BlackBerry (10), Palm (14), and Windows Mobile (13) users' phones combined and significantly more than the average Android user (22).
Games played a large part of apps users were downloading, with 65% of users reporting having used them in the last month. More than half of the users surveyed also identified social networking, news and weather, and maps or navigation apps as apps they recently used.
Facebook was the clear favorite on all smartphone platforms for social media, but was also the top app on nearly every platform in terms of reported use. Google Maps and the Weather Channel were also very popular across platforms.
Individual platforms also had a unique favorite app: iPhone users frequently used iPod and iTunes, while BlackBerry users were unique in accessing ESPN and Android users were using Google Search more, all of which reflect the user demographics and apps available for those platforms.
Nielson predicts smartphones to overtake the market for simpler feature phones next year, indicating the popularity of mobile apps will only continue to grow.