Couple of quick examples off the top of my head: - changes in configuration statements - changes in configuration defaults - removal of functionality - file

Couple of quick examples off the top of my head: - changes in configuration statements - changes in configuration defaults - removal of functionality - file format changes - major architectural overhaul (maybe the functionality is still the same, but you still want to verify that yourself before deploying) User acceptance testing is not just for software manufacturing, it can be done wherever the users are, and some companies take this very seriously.