Does Priceline usually save you money on air fare?

I usually go to Los Angeles, CA from Columbus, OH every 3 or 4 months. Cheapest air fare I usually find on a good month is $230—$240. Other months it’s around $270—$290.

I hear that on Priceline you can name your own price and they decide whether or not they accept. My questions:
Do you usually get a deal?
How much should I bid off the original price (what percent)?

Let me know your experience =)