But the value of the site is solid. I have paid $29 for hotel rooms using the site, and $17 a day for rental cars. As long as you don't have your heart set on a single property, it can work.
Still, you should never bid on something blindly. A number of online message boards are dedicated to revealing what other people have gotten on Priceline. Go to a few of them when you start your search and find out what prices worked for others, and which places they got when they bid.
One of the bigger ones is called BetterBidding.com, which is active, well-stocked with morsels of recent victories, and generally welcoming. I like to start here.
A second choice is one of the longest-running and most frequently updated sites, Biddingfortravel.com. This site has the significant downside of being run by an abrasive administrator who incessantly insists you earn her commissions by bidding through her affiliate website. (Some readers report being banned from the site if they post there without having used her website. You can simply read BiddingForTravel, and cull recent winning bids, without being singled out.)
A newcomer, WinningHotelBids.com, is just now getting its legs, and BidlessTravel.com also has a smaller selection of successful examples, but its design shows promise.
Whichever site you use, make sure your price quotes are relatively recent. Every few weeks, Priceline's stock rolls over and so reports much older than that won't be of use. And remember that hotels with four or five stars also often come with "resort fees" of around $15 a day, and parking fees that could be even higher. So the best bargains, the ones where you'll actually end up paying what you bid, are for hotels with fewer stars.
If you want these sites to remain useful, post your own bidding results on them. You gotta be a friend to have a friend.