I have been eagerly following the discussion leading up to and following the iPad annoucement. I have envisioned just such a device since held my first iPOD Touch (since replaced by an iPhone). At the time I thought “great device but Iwish that it had a larger screen”.
I think that the iPad is a new category of device meant for people who already have a computer (either desktop or laptop) and a mobile device (smartphone or otherwise) and is looking for a lightweight device for basic functions (email, web browsing, light work processing). The iPad will be what netbook tried to be … an inexpensive, lightweight, light duty computer. It will NOT replace either an iPhone or a laptop and, hence, doesn’t need some of the same functionality.
My plan is to buy a Wi-Fi only iPad and tether to my iPhone when not in Wi-Fi range. I think that Apple will need to think about better integration between iPhone and iPad. I will always carry my iPhone but won’t always take my iPad. Hence, some means of easily sharing data and connections is required.