Customer would like to have the ability to apply logic to the subtotal(s) and grand total(s) so it do different things compare to how the content is calculated in a Cross Table visualization.
For example, can I have my content calculated by Avg(Something) but for my grand total, I do Sum(Calculated Column) instead of Avg(Calculated Column)
Our users often want both a SUM total and AVG total, would be nice if they could have control to have multiple Grand Totals and choose the aggregation type. So Grand Aggregations, I suppose.