bascule, for phones it is a different matter. But my point was that for productivity purposes (and the iPad is simply too big to be directly compared to a phone) I cannot see it being more efficient. Imagine correcting papers. I can sit in a plane, draw circles around stuff that I like to have changed make a few sketches about how the graphs should look like and hope that someone can read me handwriting (or let the software try to figure it out). That does not work with touchscreens. If I was only texting, well yeah then I wouldn't need it. The only disadvantage a convertible has (again, it comes with a touchscreen) is that it is heavier than an iPad.
But then the question is what the iPad may be for. In the current iteration it is not a good working platform, too big for a mobile replacement. It may be ok for a reader, but bloody expensive and harder on the eyes than e-ink.