My feelings regarding the ipad are similar.
I know Steve wants us to think that the ipad falls completely between the iphone and the macbook creating an entire new niche, and he is mostly true. If you are a super techie or super rich this provides a terrific set with an iphone, ipad, macbook, and imac. You'd have it all. All needs satisfied
Although the average consumer doesn't have enough need (or money) to rationalize getting all 4 of those computer-like devices. A more typical approach is to buy 2 or 3 of them.
IMO the iphone (or whatever smartphone of preference) is an absolute must. the ultra-portable computer capable of doing whatever you need on the fly. You will always have your phone with you.
Now next I feel like the average consumer will basically feel they are presented with two options.
1) JUST buy a macbook. This offers a complete computer in a portable setting
2) buy an ipad and an iMac. This offers a very suitable solution for on the go, but while at home you can still do heavy duty computing.
Yes I know for option 2 you could get a macbook instead of an imac, but I just feel that there would be too much overlap between the ipad and the macbook. I like to make the most use of my money and I would feel like it would be a poor allocation of my funds to buy two devices that work so similarly when I could buy an iMac which functions better for the "full computer" experience.