iPad is not the best. Massive, rapid text entry on an iPad sucks. I took an iPad and a cr48 to the a big orthopaedics conference last week, and the cr48 was the hands down winner, using nothing but qemacs. Fundamentally, on the ipad, character recognition or dictation would be best, but I can barely read my own writing sometimes! The iPad would be a lot better if the input precision was as good as the output resolution. If you've tried any drawing apps on these things, you know what I mean. Wacom tablets have much better input precision, or at least they seem to. I want Pilot G-2 0.5 mm black speed, precision, and reliability. Right now only a keyboard comes close.
Keyboards for the iPad already exist. The future is a touch screen, and an external keyboard (probably should also mention big screens, with gpus, hooked to iPhone docks, in order to offer a fully personalized desktop experience, running off your mobile device.)
CR-48 will not be able to detach from keyboard. Everything will be designed to support a touch screen interface; input devices will be external.