I wish it was more widely supported. Unfortunately, the only worthy implementation is in Ruby (AsciiDoctor), which is what all the other projects (in Java, Python) use.
AsciiDoc would see more adoption, I think, if independent implementations existed in other languages.
I found it better suit for long form content than, say, markdown, due to the fact it has more language grammar for things like chapter, admonitions, etc.
1. Its readability is not very good. There is too much non-content text for me.
2. The grammar set is not small and natural.
The tooling is a bit of a pain, but the Java world has pretty good integration (gradle, intellij)
(except the master's thesis, which I did with latex)
That said, I would choose AsciiDoc every single day without hesitation over Markdown the minute you are talking about documentation or any sort of technical writing since Markdown is far too feature poor & buying into one specific fork is locking you into incompatibility & other headaches/compromises.