I have on two occasions.
1) At BWI, there were zero ticketing/check-in US Airways agents working the preferred line and only one other US Airways employee checking in bags for a line of 50+. I waited in line with a few other elites for at least 15mins till we got service.
2) Being denied access to the Lufthansa business lounge in Munich last weekend because apparently my US Airways Chairman card was nothing more than a baggage tag. Also the lady did not believe my status as a *A gold applied there. I was embarrassed in front of the line behind me. Angrily tweeted US Airways, Star Alliance, and Lufthansa a big ... for the disrespect I received.