When you customize the "Partner Commissions Pending Authorization Detail" commission report, there are payment fields available (e.g., Pending Commissions: Payment Transaction: Transaction Total) which show the amount paid by the customer.  Great, exactly what I needed, I love it.

But - these payment fields are only available on the Pending Authorization reports, not the Authorized or Paid commission reports.  The only thing I could find was:
[LIST]
[*]Payment Method - not very useful without the payment fields, though
[*]Payment fields for the Paid commission reports (see Paid Commissions: Payment: Total (Transaction)- but this comes up with the total commission paid to the partner, not the amount the customer paid.  And it's redundant anyway, since there's already a Paid Commission field on the standard report.