I scanned my blog for retropay. I found back a post of september 2003. At that time we worked out in the Netherlands a solution around reversals. Standard retropay was not an option at that time, since the specifications of the customer were too specific, volumes were huge, and the NL localisation and core solution were not yet 100% finished.
Q: Would i do it again, more then 3 years later?
Main reason is performance. Retropay is designed to recalculate exceptions. When massive retropay is needed, you can start it very early in the payroll cycle. And run it an other time to process the last minute exceptional cases.