"...the percentage of e-book consumers who exclusively or mostly purchase e-books fell from nearly 70% in August 2011 to 60% in May 2012. Over the same period, the percentage of survey respondents who have no preference for either e-book or print formats, or who buy some genres in e-book format and others in print, rose from 25% percent to 34%."
The article also notes that the Kindle Fire has overtaken the iPad among ebook consumers. No surprise there, though iBooks remains my personal preferred reader. I am hopeful that iTunes will eventually include ebooks in their iMatch service so I have Cloud storage for my non-iBookstore purchased epub titles.