This guy says it better than I could.
Keeping that in mind, Richard Stallman's missive on the subject just riled me up:
Proprietary software keeps users divided and helpless. Its functioning is secret, so it is incompatible with the spirit of learning. Teaching children to use a proprietary (non-free) system such as Windows does not make the world a better place, because it puts them under the power of the system's developer perhaps permanently. You might as well introduce the children to an addictive drug.
Oh, for fuck's sake. You really just employed a simile comparing a proprietary OS to addictive drugs? You know, ones causing actual bodily harm and possibly death? Really, Stallman? Really?
If proprietary software is half as good as free software at aiding children's learning, you're damn right it makes the world a better place to get the software out to children. Hell, if it doesn't actively inhibit learning, it makes the world a better place. The problem is that Stallman doesn't appear to actually give an acrobatic shit about learning, and sees OLPC as a vehicle for furthering his political agenda. It's shameful, the lot of it.