There was an article from the New York Times yesterday about play with digital media.  I think they’re referring mostly to games (hence “battling alien invaders” ).  No mention of educational apps or ebooks, but there are a few good sound clips:

Playtime is not wasting time, regardless of format. Play is an essential part of the work of growing up. With digital media, children learn by interacting with others, following rules, trying on new personalities, competing in games of speed or strategy and exploring new environments. They can build social, cognitive and physical skills from social networking, watching videos and battling alien invaders.