ReportBuilder is very powerful, but for us lacks two key elements from the SiteCatalyst UI....
1. I can specify a number of ranked records to pull, but there is no way to get the report total that is provided on the bottom of every SC report page.
2. As stated in another idea for the SC interface, we need to also access the total number of line items, or unique entries, in any report from within ReportBuilder.
I completely agree with #1. Sometimes I know there are going to be more than 50,000 records returned in a report, but I still need to have the grand total of all records for that variable (without specifying the top "n" instances), in order to calculate an accurate % of total in an automated fashion.
With the new calculated metrics release from last year, you can now use the countof() function to get hte number of unique values for a given dimension.