Handset maker Ericsson conducts research on consumer behavior and attitudes all over the globe with thousands of consumers. Not long ago it released findings from some early 2011 research about smartphones and tablets with a specifically US audience.
There are no dramatic findings or true surprises but each piece of research contributes to a more nuanced picture of the market and consumer behavior. The data reflect self-reported usage patterns with an emphasis on time of day. Here are two of the charts that show usage of smartphones throughout the day:

The following chart reflects the comparative "daypart" usage of the mobile Internet and GPS apps (probably maps in particular): 
In terms of tablets, Ericsson found that demand was higher than for most other electronics and devices.

Finally the data show that tablet usage patterns parallel those of smartphones, rather than PCs, although tablets are "cannibalizing" PC usage to a degree. Other studies and data reflect different usage patterns for tablets, however.