I'm near 100% leisure, always on my own dime and definitely partial to Priceline (to give you an idea of the typical budget, Motel 6 was starting to get too expensive for me. In many places they cost double what they did 8 years ago).

Many of my hotel stays, especially in the U.S., are in conjunction with mileage runs. I just can't justify to myself flying someplace and then flying back, so I always make a trip out of it. Typically 3-day weekend, rent car at weekend rate with a free day coupon, hotel through Priceline.

That said, though, there's one frequent destination where Priceline usually falls short: Las Vegas. I always try PL, but it might come through one time in 4 (For LAS I try to pay $15-20/night and top out around $30). Usually the third-party sites like tripreservations.com and Expedia and the websites of downtown casinos will have something PL just can't see to beat. You also have places like the Sahara that you might get through PL that will gleefully charge an extra $3/day energy surcharge, or Palace Station and its $4.95/day "hotel services fee." Seems unfair to me that these guys are on the same footing to take your bid as places that don't charge those fees.

As an aside, cheapovegas.com's "Hotel Bargain Bin" is filling with reports of people landing $10-15 rooms at pretty decent places (through their websites) in Las Vegas during the December dead weeks. Check it out.