It can't be the "do anything" device - if I still need 2 devices to get my stuff done, I might as well buy one that's less expensive and will give me the same function I need.
I do think Ben built a bit of a straw man out of Nadella's comment, though.
> "Nadella is basically saying Microsoft needs to make Surface because Microsoft makes Surface."
That's a very selective interpretation of what Nadella said. He said he wanted to integrate the company's products into a single experience. He didn't say that's why the Surface exists, nor did he say the reason behind building hardware and products is for the sake of integration. He's just saying the vision is to integrate the experience. Ben makes it sound like there's no other reason behind it, but Nadella may very well see reasons for integration that he didn't go into (there).