Personally, whilst I'm a great fan of my Nokia E63 (Blackberry clone) for many other applications - particularly met and NOTAMs, I am a particular fan of paper in the cockpit - although I keep playing: I'm going to have a go at checklists on my Sony Reader sooner or later, and there's a remarkable amount can be done on a Garmin.
On the other hand, I've just come back from two flight test conferences in the USA - at one the University of Tenessee showed that they were successfully displaying and recording flight test data streamed directly from an instrumented King Air, and in another Lockheed Martin showed cockpit video from the rear seat of an F-16 twin sticker which was recorded on the observers iPhone after the HUD video failed. The potential there is definitely enormous!
G