Good day.  I am the author of one of the blogs linked above and noticed you in my referrer log.  Someone was asking what typical return rates are in the shareware industry.  Speaking only of my own experience, for mature software versions I experience somewhere south of a 2% return rate (my total lifetime return rate is about 5%, which is a function of a relatively high number of returns for the first release of my product, first release of the Mac version, and two updates which did not go smoothly on machine configurations I had not anticipated).  I made a blog post talking about this in more detail which some of you may find interesting.

http://microisvjournal.wordpress.com/2007/02/05/rates-at-which-shareware-customers-request-refunds/