Well, the annoying thing is that it "should" work for car rentals. Like most frequent travellers, I find the airline portion useless, because I have to much brand loyalty (think ff miles) and routing/scheduling is too important to let priceline pick it (I'd also note that priceline isn't saving folks much money on airline tickets these days, either).

But car rentals would seem like the perfectly "fungible" commodity. While there can be differences in the at-airport service -- and member cards that let you bypass the counter are nice -- the cars themselves are all pretty much the same. I think most of us would be willing to use priceline for cars if there were true discounts.

But they simply aren't there. I just tried another couple of cities and I couldn't save $5/day on any of them. That's pretty useless, IMHO.