I used it one time about two years ago for a last minute flight from our local tiny airport. It was for a funeral so we only had a few days notice and only one person was flying.
The lowest price was around $1000 from all other sources. I got the ticket for around $500. My initial bid was not accepted, they came back with a counteroffer. They gave me a Delta flight, it had one connection and was mid day.
They won't give you a red eye or a flight with more than one connection unless you approve it.
My husband recently had to fly to a funeral, but in his case we ended up going with a Priceline exclusive. If you search for flights in their search tool, they may list a Priceline exclusive at the top. It's similar to the name your own price, but they give you the price, number of connections, and a 10 hour departure time window up front. Once you book you get the rest of the flight details like airline and arrival time. We saved $400 using that option for his flight, even when looking at discount airlines and looking at all airports within a 3 hour drive. His flight times were fine. It did have tighter connections on the return trip than we would have picked, but it turned out okay.
I won't use this type of tool for a family vacation, but it's great for last minute stuff.
Priceline has great rental car prices too, and you don't need to bid to get those.