I have had GREAT luck with Priceline!
Honestly, I can't think of a bad experience, and I've probably had 20 Priceline stays, over the last 3 years. And helped many family and friends with successful bids. Some of the deals I've gotten have been phenomenal!!! But you do need to know how the "system" works.
With Priceline, you are bidding on a certain zone and a certain "star" rating (quality level of hotel). You can't single out a certain hotel. But, you can never get a hotel that is less of a star rating than you've bid on. (but you can get a higher star rating). You also guaranteed a hotel in the zone or zones that you are bidding on.
The most helpful thing for me, is a certain web site, where people post their winning bids. By perusing the bids, you can see what hotels are offered in certain zones and what $$$ amount it takes to get a winning bid. It's not full proof, but if you do your homework, you're much more likely to have a successful bid. If you'd like the link to the website, just PM me and I'll be glad to help you.