LibrarianbyDay shared this on Twitter today: Results of the Kindle Nation Winter 2011 Citizen Survey
Some items worth noting:
93% of respondents were from the U.S.; only 3% a resident of a country other than the U.S., Canada, or the U.K.
70% of respondents are earlier adopters of new technologies, so there is much potential for growth
Reading on Kindles: A superior experience 4.9/5 rating
A majority of users are interested in free books