It has great usability both for creating content forms and for end users, however for the more advanced users it lacks alot of documentation.
The documentation provided is very basic, and even if you subscribe to a membership, the forum isnt much of a help either.
The general attitude is "look in the code and see for yourself", and i have the impression that the ZOO team members who are active in the forum are not developers but only end users.
To sum up, this component is great for the average user, but if you are a more advanced user, be prepared to read alot of lines of code to customize the component to fit your needs.
And the support is absolutely amazing, any request is replied in a few hours or less.