Workflow engines have gone mainstream: Just take a look at Windows Workflow Foundation (WF). Microsoft is giving it away free, bundled with .NET 3.0. Normally, workflow engines can cost upwards to $50,000.

While business workflow engines can undoubted allow the system to be more flexible from a business process perspective, they are fairly involved to integrate into the system. Engines that provide a Workflow Designer ease the development effort, but debugging a workflow process gone wrong can be quite an experience. With each worklfow engine, there is potentially a different process definition language, such as OpenWFE's (http://www.openwfe.org/). If you stay with the Business Process Execution Language (BPEL) standard, the number of available engines is daunting. See http://en.wikipedia.org/wiki/Comparison_of_BPEL_engines.

In the long run, an integrated workflow engine will save you money when more and more business process changes are demanded on your system. The business process is loosely-coupled from the technology, which allows for a flexible change system. You take the development hit upfront, and reap the benefits later. Last time I checked from a total lifecycle perspective, sixty to eighty percent of costs occur after development and implementation, into maintenance.