And they should NOT charge you the $5 fee for using a res agent (and mailing the cert in) or the $10 fee for buying the ticket at the airport - because you cannot use the cert online.

I just used to Customer Service vouchers to pay for parts of two tickets at DCA. When I made the reservations, they said on the phone that those fees would be waived. I expected a fight over it at the airport ticket counter - but there was no problem.