One of the features of Mules ESB, that I find very useful, is the Mule Expression Language (MEL). It can be used not only for flow control and filters, in fact most of the components and transformers that come out-of-the-box with Mule ESB support that properties are specified using MEL.
In Mule ESB 3 they introduced the concept of Configuration Patterns. These patterns helps you simplify some specific but common integration scenarios.
Instructions on how to build Mule ESB 3.3 from source
When building integrations with JBoss ESB you naturally need to interact with other systems via notification gateways other than messaging queues. It could be that you need to enrich data from a WS-SOAP service or just put data into a file in a specific directory. These addresses and location often need to be different depending on which environment you are running in.