I disagree. This sort of device has the very real chance of killing notebook computers.
I don't think that desktops are going away any time soon, for two reasons. First, if you are going to work for hours at a time, a big screen and keyboard re far more comfortable and practical. Second, really significant work requires the horsepower of a full OS (as opposed to apps on this device).
That said, most people don't need a full computer to travel with. They want something light, with an "always on" connection to the cloud. They want to browse the web, check email, play a game, read a book, listen to music. Sure, maybe they can tinker for a bit with a document too.
Will 90% of the world miss the openness and power of a full computer? I doubt it. And god knows that the screen and multi-touch already beats the hell out of most netbooks. I think it's a no-brainer that this thing will be wildly successful, and I do think it could (over time) kill off the laptop market. (Not for developers or hard-core geeks, but for (so-called) normal people.)