Campus Technology is reporting on this research effort.
… 2,000 students enrolled in 14 introductory psychology sections were given the option of purchasing a bound, print copy of the new textbook for $134 or selecting an e-text version for $50. Since the text used in the study was new, there was no option for buying a used edition. Ginn said the study included traditional-aged students (18 to 24), non-traditional students, students taking courses in the classroom, and students taking courses online.
The survey found that 22 percent of the survey participants purchased the e-text, and that 41 percent of those e-text users reported preferring a digital textbook to the traditional hard-copy textbook. Students in online sections were slightly more likely to purchase the e-text. Traditional-aged college students were 1.73 times more likely to purchase the electronic text than students 24 years or older.
Thanks to Michael von Glahn for the link.