"...despite being a key information for API users, most usage patterns are not described in official API documents."

Its a great point, however I feel that any API that provides a demo project is pretty much accomplishing this better than words ever could. While I, almost, always read API documentation, I often find the picture is only complete when I've either started to use the methods myself (feeling out issues around authentication and the format of the response of the API) or after I've been hands on with the included demo project (when one is included).

Also minor annoyance: I love that this is a free service, but PeerJ's download button needs to be moved to a slightly more obvious location.