I had a wierd experience with priceline trying to find a hotel at (or near) YYz airport. I bid $36 for a night in a 4* hotel. They didn't accept. then I bid $31 for a 2-4* hotel a minute later, and got a 4* Wyndham!?! Overall good experiences with them though.
Tip: don't bid in multiples of 5, but always add a dollar...increases your chances of being accepted(at least in my experience). So for ex. bid $21 instead of $20