This sounds like special pleading - so now we have to wait another decade or two before we're allowed to pass judgment? What sort of effects are you expecting to pop up then, that we can't observe now over a sample of <850,000 laptops?
I think giving computers to children is a long game. It is unreasonable to expect short-term miracles, but for example I probably wouldn't be programming if we hadn't had computers available for playing and exploration when I was a kid. But from that time it was nearly ten years before I did anything productive with them...
There are a few other studies on this matter both indicating effect and lack of effect of the OLPC in Math and Literacy (this study mentions them in introduction). Apparently, the OLPC has not produced very good results in Literacy and Maths in Peru and its use must be reviewed but changes in education always take a long time to produce results, sometimes as much as a full generation, and depend on a number of factors.
As for the long term effects: I expect that the children that had access to the OLPC will have a measurable advantage in the labour market when compared with children that did not.
