AsciiDoc is not as widely adopted as Markdown, but it’s used in some pretty serious places. Here are a few notable examples:
O’Reilly and MakerPress
Clojure Cookbook (AsciiDoc source)
GitHub supports AsciiDoc syntax in repositories, wikis and gists (powered by Asciidoctor)
NFJS, the Magazine is produced from articles written in AsciiDoc
Context and Dependency Injection for the Java EE Platform (CDI)
Specification (AsciiDoc source)
Website (AsciiDoc source)
Golo Programming Language Guide (AsciiDoc source)
Neo4j graph database project (AsciiDoc source)
Phusion Passenger Users Guides (AsciiDoc source)
Git user manual (AsciiDoc source)
Enterprise Web Development: From Desktop to Mobile (AsciiDoc source)
Bintray REST API and User Guide
These examples are more than just testimonials. They should give you ideas about how to be successful with AsciiDoc for your own project.