The iPad is the perfect device
We got an iPad a few months ago and I still can't say enough good things about it. I have found that I want to have it with all of the time now because of it's utility for many activities. For example, on a couple of recent long flights (I was in the cabin and not the cockpit unfortunately), I used it for reading (Kindle library), writing (trip journal), photo editing, drawing and sketching. The battery life was never an issue and the performance is excellent. This was all without Internet access during the flight as well. I think that it's a given that, like hotels, airlines will soon find that providing Internet access during the flight is expected and in many cases necessary. If I had to choose between two different airlines with a insignificant difference in price I would definitely go with the one that provided connectivity in flight (as well as waiting at the gate).
Retailers will also find that the iPad or tablets in general will provide a enhanced experience for their customers and that customized apps are to their benefit for advertising for in-store sales, navigating large store spaces or just providing additional information about the products of interest.