I have integrated jBPM in a logistics application that I am currently working on (screenprint http://www.vankessel-it.com/real/files/Project7.png). So far I am very happy with jBPM. It makes my job easier and adds real value to the application.
In the last year we had a project during our study at the FH-Joanneum where we had to implement a business process management engine into the e-government plattform of our city council in graz. http://www.graz.at
we evaluated enhydra shark and jboss jbpm but finally we thought that the jboss solution was the best for our needs. some reasons were that jbpm has the better documentation and a bigger community.
today the plattform should already run with jbpm, here is the link http://egov.graz.gv.at/
We as well chose jbpm over some other products due to the active community and we thought it had more documentation. We have worked fairly hard trying to get it to work though, adding an RMI wrapper to allow it to be called and controlled from within the Oracle db itself.
It is implemented for a large university work flow system here in Texas. It will initially be used for document processing within the Administrative Services, but we also have some forms we are going to use in a lab wide exposure over different groups in a 500+ environment.