I fly small, single pilot, piston airplanes and the ipad has done wonders in keeping the cockpit organized and efficient. Many separate applications, not just pdf's, have already been made for the pilots. Sporty's has one for airport diagrams and plates. I use JeppView, a product of Jeppeson which provides all the plates I need for instrument flying plus enroute moving maps. It's such an improvement from carrying around all the paper, and the the best part is now everything is updated automatically, so I don't need to worry about carrying expired plates.

I believe JeppView is FAA approved, but don't think the ipad is...yet. Since what I have read Alaska isn't using them during t/o or landing, I think that they are using the ipad more for airplane checklists and non-route specific operations. In the future though, I could see them getting and using the Jeppview software, but it would only make sense if it could be used during t/o and landing.