We are a small telecommunications company that provides phone service to about 20,000 customers. We have JBPM in production to handle high level order flow for several types of order. This includes order scrubbing as well as integration with our provisioning and billing systems. Each order process defines about 15-20 states--some of them are human tasks, and some are automated.
We've been quite happy with JBPM, and we're continually identifying new processes for management with the engine. In fact, in our organization, if it had not been for JBPM we wouldn't be using a workflow engine.
To answer one of your questions, JBPM has no inherent "value" related to integrating systems--it is not an integration platform. However, JBPM has tremendous value in orchestrating processes.
We are also trying out JBPM as a workflow engine in a high volume environment. I'm curious as to how much throughput can be achieved.
Have you tried running performance tests to see how many workflows per second or minute it can handle? What type of hardware are you running it on?