I've never used the tiny keyboards on smartphones, so i figure my learning curve will be not so steep. Just getting used to the "iPhone way" and thats it.
For those used to a conventional small keyboard, it may be more difficult, but most likely people will learn to love it.
I don't think the soft pad will suffer much vs. a smartphone keyboard. I'm more concerned it might suffer as a traditional phone keypad; I do not know how I will find a hotkey without looking, for example.
Whatever, Mossberg is sure to give it a fair review.