I am currently experiencing the same problem redeeming a certificate as marcokatz. I volunteered to be bumped from a flight from San Juan to Philadelphia and was given a certificate for a free flight anywhere in the US, Mexico, Latin America or the Caribbean. Alternatively, I could get $ 300 off of a US Airways flight.

Good luck to anyone trying to use to redeem the certificate for a free flight. I tried multiple dates to multiple destinations - none of which were available using the certificate.

Additionally, just as the initial poster indicates, the $300 voucher is not good with certain fares (I believe mainly internet specials). I would have had to book a significantly higher fare to get the $300 off, resulting in my certificate being worth only about $150. I didn't do it (I ended up booking with another airline for a significanly cheaper fare)and am still trying to figure out how I am going to use my certificate, which has to be redeemed by early July.

It has been a very frustrating experience and leave me with a negative view of US Airways.

My husband and I were departing Chicago on US Air and while I was in the restroom it was announced that they were overbooked and offering $300 to be bumped. My DH thought this would be great since the next flight was an hour later. When he went to volunteer it turned out it was a $150 voucher( each) OR $50 cash. We said no way. It wasn't worth it and now I'm glad we didn't do it

My brother-in-law always referred to them as USeless Airways also as up until recently they were still America West which we had no trouble with.
Agree with getting vouchers instead when possible.