A friend shared this story (from a different link posted by Mashable) on Facebook, and I asked then how we really know how well the students are picking up what knowledge of what topic through this means. I see, going back to that link (the same text appears in your link),
"In an interview after his talk, Negroponte said that while the early results are promising, reaching conclusions about whether children could learn to read this way would require more time. 'If it gets funded, it would need to continue for another a year and a half to two years to come to a conclusion that the scientific community would accept,' Negroponte said. 'We’d have to start with a new village and make a clean start.'"
I also noted in the Facebook discussion thread that National Public Radio in the United States recently broadcast a report about One Laptop Per Child in remote villages in Peru, where ensuring access to the Internet or even electricity was a difficult problem for the schoolchildren attempting to use the laptops. I think further research is needed before we can be really sure that dropping off the laptops next to groups of children in the Third World will genuinely result in learning gains for the children in the usual school subjects.
AFTER EDIT: An astute top-level comment below asks,
Nobody's actually there, so who knows what's going on?
And, indeed, I should have mentioned that to properly evaluate this project, you would not only need people in-country, seeing the children face to face, but you would have to make sure that the evaluators are familiar with the local language, as foreigners who visit another country without knowing the local language often miss many important details in their interactions with local people.