The MessageActionGuide should describe all the actions we support and the ProgrammersGuide should describe the transports/providers.
Could you explain further what you think is missing?
In answer to your explicit question, drools is used by ContentBasedRouter/Wiretap, BusinessRulesProcessor and MessageFilter.
You can also use XPath expressions for CBR too, via Drools.
I came across a reference to this "MessageActionGuide" in chapter 10 of "Message Transformation" of the Services Guide (PDF), but I am not able to find this guide. I'm using JBossESB 4.8. Can you point out where this is? It's not in the docs folder of my dist which is where it was stated to be on the forums / discussion groups. Does this guide still exist? If not, where is the content now?