In the excitement of working with rules engines, that people forget that a rules engine is only one piece of a complex application or solution.

Because rule engines are dynamic, in the sense that the rules can be stored and managed and updated as data, they are often looked at as a solution to the problem of deploying software (most IT departments seem to exist for the purpose of preventing software being rolled out). If this is the reason you wish to use a rule engine, be aware that rule engines work best when you are able to write declarative rules. As an alternative, you can consider data-driven designs (lookup tables), or script/process engines where the scripts are managed in a database and are able to be updated on the fly.