I just used Hotwire this last weekend for a week's rental of a full-size car at $8.95 a day plus taxes, about $120 total. I didn't need a full week but it was cheaper to get the better rate and turn it in early.
I got an Alamo car at MCO, which might be slightly cheaper than FLL. When I collected the car, they had minivans available for the same price. Keep in mind that the last weekend is traditionally one of the slowest travel weekends of the year -- my nonstop flights from Bloomington, Illinois to Orlando were only $89 each way on AirTran.
Normally, I look up the car price on Hotwire and then reduce it about 20-25% and bid on Priceline, eventually beating the Hotwire offer. This time, Hotwire was so cheap, I didn't even bother.
Both Hotwire and Priceline use Hertz, Avis, Enterprise, Alamo, and Budget, as I have had cars from all of those. The only time I haven't found the cheapest rate that way is during peak periods like Christmas, when I have sometimes found dealing directly with a rental car company, using a discount code, to be the best.
Edited: 10 February 2012, 8:18