We've implemented one BPM project using WDJ and CAF.
Currently I'm switching for some User Interfaces to SAPUI5.
I come from the ABAP world and I must admit that it's really frustrating to work with SAP's BPM platform.
It's so damn unstable: If you deploy something, you've to cross your fingers that everything is still working afterwards. Here I'm talking especially about the "Application Communication" section in NWA!
So often I had to deassign profiles, assign them again afterwards etc.
It's really a mess!!!
The same happens if you change a web service interface and reimport it into BPM: Sometimes it takes ages to get everything working again...
The idea behind the BPM engine is nice, but let's be frank:
SAP in combination with JAVA just sucks!!!
It's just frustrating...
I've lost so much time for implementing this process.
And setting up NWDI/CTS+ was really a pain. It took me weeks to make it work.
If you use SAP WAS JAVA, you really appreciate how stable the ABAP stack is!
I would rather choose SAP Business Workflow now although our implemented process is not related to SAP ERP.