rmccamy: Not to create thread drift or wrong board posting, but I'm curious about the 'draconian" rules you refer to on UA VDB vouchers. I've been bumped a dozen times and had no restrictions on their vouchers insofar as purchsing domestic tickets.
The key difference with UA vouchers and AA is that if the total UA bump compensation is for $200, you get four $50 vouchers. If you are purchasing a $120 ticket and use three of those fifties, there is no residual given back for the $30. The solution is to use two vouchers and $20 cash/credit card, keeping the remaing two vouchers for another ticket.
Recently UA has been offering a free round trip ticket rather than vouchers for VDB; vouchers are supposed to be available on request but some agents apparently decline to give them. There are serious restrictions on the use of the free ticket, including 14 day advance purchase and limited availability. While most FT participants prefer vouchers (because the ticket you buy with them earns more miles, the free ticket does not earn miles) there are numerous reports on the UA boards that infrequent fliers love getting a free ticket for taking a bump and UA is getting more than enough volunteers in their oversold situations.