I used them for a trip this past weekend just to get from CLT-PHL, a route I thought I knew every trick to flying. They saved me between $75-$100 for that simple flight.
What impressed me though is that they found a flight that I could not find on the airline's website. I don't know if it was a code share flight with some other airline but I looked all over USair's site for the flight I bought from some random discount site and could not find it.