Response to my own post (with help from Xceed’s tech support):
I discovered the key to the (lack of) performance. My very large report used the “%TotalPages%” field in it. When this field is included in the report, the report generator silently generates the whole report in order to get the accurate total number of pages. This occurs before the “Generate Previews” dialog box appears.
Without that field, the “Generate Previews” dialog box does appear immediately, no matter how large the report is. But when the field is included in the report, there is a delay before the report generator provides any feedback at all.
Imported from legacy forums. Posted by AlphaGuys (had 6220 views)