On one project we are looking at where to implement workflows.Does anyone have experience with both FileNet and WPS (or know of any studies), that could say anything about the amount of effort required to create a workflow in the 2 products? 
Productivity comparision FileNet versus WebSphere Process Server
productivity
Do you mean the old Websphere Process Server or do you mean the current product: IBM Business Process Manager (aka IBM BPM)? Although the latter is the direct successor to the former, the IBM BP is much more focused on speed of development because of the functionality that was added from the Lombardi acquisition. (Disclaimer: I worked for Lombardi so I'm not unbiased in this assessment.)I know more about IBM BPM than FileNet, but I would generally say that it would vary pretty widely on the type of process you are trying to implement. A project that is very document centric is going to be easier to develop in FileNet. A project that is very integration or human interface centric is going to be easier to develop in IBM Business Process Manager.