iPhone sales were apparently 57 million units over the first 24 months. This is a popular device, but Apple still has less than a 20% share of the smartphone market. Figures from
here.
My point is not pro- or anti- iPhone or Apple, but simply that while they are significant they are not, at present, dominant in that market.
My view of the iPad, FWIW, is that it is an excellent user interface looking for applications. Whether it succeeds is, I think, a matter of whether people come up with compelling things to do with it.
As I've already mentioned, reading books is not, for me, an appropriate application for this device due to screen type and battery life. It might be great for something else - the photo sharing looked good, for example, but it's an expensive way of getting a glorified photo frame.