Plenty of times. I would say I win tickets at my bid price probably about 35% of the time. Just depends on the seller. Some are season ticket holders who just want at least something for the ticket.
The additional fees are a little annoying on top of the ticket price, but no different then Stub Hub. The convenience can't be beat. You just give them your DL or credit card (I give them my DL) at the door, they swipe it, and print out your tickets then and there.