I've used priceline over 100 times probably. Its great once you know what you're doing. Use betterbidding like was mentioned above and learn how to use "free re-bids" where you include zones that you know don't have the higher star hotels.
For work, I usually get $55-$60/nt for a 4* Houston Galleria area, $60-$70/nt for 4* Downtown Houston, and 4* in downtown Dallas for $45/nt.
I've also used it in NYC, Boston, Denver, and San Fransisco.