I was setting up a pptp tunnel today, so as a result I was also glued to pptpclient’s documentation. I was really impressed by the quality of writing and comprehensiveness–there is even a Gentoo howto.
One of the most interesting parts of the documentation was the fault tree section of the diagnosis page. It provided step-by-step troubleshooting that was informative and completely accepting of failure as a possibility. Most docs I’ve been through typically present the happy case first and foremost, while furrowing some possible exceptions into an FAQ, seemingly as an afterthought. Using fault tree analysis here, the pptpclient devs made their software much more user-friendly and usable. I hope to see this pattern in more future projects!