A new report on free and proprietary software in public computer labs in Africa is out from the good folks at bridges.org. Skip down to the "Key ground-level findings" for the buzzword-laden summary.
From my experience in Namibia, I think their findings are mostly accurate. Free software has historically worked well only in well-planned, well-supported installations. You can always find random people to administer an isolated installation of windows 98 boxes; linux expertise is much harder to come by. And it is unfortunately true that most computer labs are not sustainable. Do-gooders from $RICH_COUNTRY drop 20 computers in a room, say "go", and then wonder why it doesn't exist two years later.
On the other hand, if well done, free software can be a liberating force in the developing world. Namibia was lucky to have Schoolnet.na, a home-grown organization that focused as much on the human side of computing as the actual hardware.