There is a lot of functionality to workflow in MSCRM 4.0 and I think the "Increment by" ability is one of those little known capabilities that can add a lot of value. One of my coworkers recently used the "Increment by" to update the number of devices an Account owned when an Opportunity was "Won." If the Opportunity that was won was for 4 devices then the Account "Total # of Devices" would increment by 4. This can be useful for Cases, Products, number of days open type calculation, etc. You can increment, decrement, multiply by or just set a field vaule all off of either a static value or a dynamic value from a field on a related form.
Great functionality that I don't see people using all that often. Hopefully this will be of use to someone out there.
Dynamic Methods Inc.