>We are looking into various ways we can sell and license upgrades for our vertical market software. Do you know of any resources that examine the options in detail? Currently, we are considering a typical upgrade cost of 40-60% of the purchase price and an annual subscription program.

Joel, you might find some good information in Whil's "Developer's Guide. (http://www.hentzenwerke.com/catalogavailability/dg3.htm).