I definitely recommend using Priceline. I got a room at the W Hotel on Lexington Avenue for next weekend for $95 a night. You can't go wrong if you only bid on 4* hotels in the midtown east, west, or south zones. Other 4*s that have come up lately include the Waldorf Astoria, Hilton New York and Towers, Sheraton New York and Towers, Intercontinental, and the Drake Swissotel.
Check out biddingfortravel.com for recent successful bids and a link for $5 in bonus money.