Have only had good experiences with Priceline both in US and abroad. Never had to cancel, but understand that if you do, you don't get your money back. What with all I have saved, if someday I pay for a room that goes unused, I am still way ahead.
An associate of mine had a bad experience in a trashy hotel (3 star claim) but then used Priceline twice in Cleveland and stayed in a lovely Doubletree. She thinks that she is still ahead. And the first experience could have happened if she had direct booked as the hotel was well located and had a decent brand.