If you go back to the original plan and purpose of the OLPC you get a inexpensive, rugged mobile computer that kids in developing nations can fully take advantage of. And while we have seen mixed reactions on the deployment of the program, critics have usually been generous as far as the XO's hardware is concerned.
But durability is one of those things that are very hard to evaluate, unless you just keep on using the thing until it brakes, if ever. Engadget reports that the OLPC XO's rubberized keyboards are literally being ripped apart, although from the information we have read on this thread, the problem has risen when young kids (5 years old or less) are exposed to the laptop and they keep on peeling the keys. If for some reason this has happened to you, thankfully there seems to be a DIY solution, given that the OLPC organization doesn't seem to be ready to supply replacement parts.