I’m a touch typist on Keyboard. If you force yourself and type a lot, you can really function quite well on the display keyboard you just have to unlearn resting your fingers on the display. I wouldn’t want to type for hours like that, but answering an email here and there, typing notes and using the type ahead word suggestions you can really get by.
Of course it depends on ones purpose of usage for the device. I have a blue tooth keyboard for when I have typing tasks that take most of the day. And, I can use that keyboard for my Mac Mini, or any other blue tooth device in the house.
A single use keyboard, however, for 1/3 of the price of the iPad, doesn’t make much since for me.