I’ve actually played with the XO (or at least, an earlier prototype) and I’ve got to tell you, these things are the coolest gadgets since they invented digital Cheez-Whiz. (There’s no such thing as digital Cheez-Whiz. That’s my point. Think about it.) They’ve got a lot to recommend them to First World consumers as well as Third World students, they’re hackable as all hell, and they’re cheap: $399 buys one for you and one for a kid in the Third World.
As a portable gadget, I’d say they’re probably superior to the new Asus EEE, which runs around the same price. I’d really recommend getting one, if you can afford it, as a laptop alternative, and as karma insurance. Hell, you might find yourself using your XO more than your regular laptop, particularly for e-book reading.
And if anybody wants to buy me one, I won’t argue. This is one of the only pieces of hardware I’m genuinely lusting over right now. I’d rather have an XO than an iPhone, if that gives you any idea.