I use Priceline very often for hotel stays. I find that, in most major cities, the zones are defined narrowly enough for me to usually be pleased with hotel locations. I generally bid 4* or higher and have always been pleased with the hotel quality.

I've only used PL one time for a flight. If you fly from a small airport (as I often do) that is served by only one or two airlines, it makes it much easier to figure out which flights/carrier you might get. I've read on the biddingfortravel message board that PL will not have you change carriers during a connection on domestic flights, so that also helps in figuring out how to bid.