Right now, aside from problem solving, he is learning to master the computer. The reading, spanish, and math software which he has is coming along barely ok. He learning also improves when we review the material outside of his computer time. Without the direct adult attention, he is focussing on what he finds important. What my first son does with the computer is great, but there is nothing which indicates to me that my second son will have the same kind of experience.
All children are unique.
So what will be a boon for one will be a hinderance for another. A tool is only worth having if it is appropriate to the task. You need a 'lab' to use desktop machines. The classroom will be effectively useless for any non-computer based work. If the computers are to be used 'ubiquitously' for parts of all classes, every classroom would have to be a 'computer room'.