I used it once (I think it was priceline, but can’t remember for sure) to book a hotel in NYC for a couple of nights. It was a great deal. My wife and I got a 4 star hotel on the Upper East Side for less than $100/night. I think if you really don’t care precisely where you stay, it can work out really well. However, if you have specific limitations, then it can be a lot more of a crapshoot.