Link to 8/15/2011 summary.
Excerpt: More than eight in ten (83%) American adults own some kind of cell phone. These devices have an impact on many aspects of their owners' daily lives. In a telephone survey conducted from April 26 to May 22, 2011, among a nationally representative sample of Americans, the Pew Research Center's Internet & American Life Project explored the uses (51% had turned to their cell phone at least once to get information they needed right away) and behaviors of cell phone owners (42% of cell owners used their phone for entertainment when they were bored).
Despite their advantages, the survey also found some downsides for owners, ranging from just needing to take a break from using it to the long time required by some downloads
Link to full report.