Worked with a rete engine in Tibco's CEP. This was used for utility events and deciding what if anything to be done with the event in the context of others and then route it. I've seen it similarly used with bank security and customer management. Another interesting use case was using it as a master data management platform for customer data across a company with a bunch of subsidiaries that had the same customers.

What we liked about it was the ability to contextualize events by keeping a history and relationship between objects and events that we could reference as part of our rules. Particularly when we get an event storm and putting more signal into situational awareness when there is a lot of noise.