Documentation is embarrassingly out of date...
Best place may be the Javadoc (has compiled examples in it) http://timyates.github.io/groovy-stream/javadoc/index.html?groovy/stream/Stream.html
Out of date usage, news, etc. can be found here: http://timyates.github.com/groovy-stream/ or http://timyates.github.com/groovy-stream/main.html
The first casualty of lack-of-time is documentation :-(