I've used it a couple of times. I found it to be 'hit or miss'. I went to San Diego once using the 'Name Your Price' for a 4-star hotel. They actually put me in the same hotel I was going to book through normal channels, but for $20/night less. I tried it again for a Ft. Lauderdale hotel, and the place ended up being a dump on the opposite side of town I wanted to stay in.
I've never tried to do it for the airfare. A co-worker used it just a couple weeks ago, and he put his price in for airfare from San Antonio to LA. On the way to LA, they put him on a 6:30 AM flight out, with a stop in Phoenix. He had a 3 HOUR layover before continuing to LA. The flight back wasn't much better. He said that he did save around $200 on the flight, and he just bided his time in the airport surfing the Net on his laptop.