First time I have heard of the Pay Now option for rental cars. Here is a good overview of it. My take:, on the other hand, is an incredibly reasonable $10 any time before. I believe others are in-between.
- It is a good development in principle, since it makes the industry more efficient, and shares the benefits with consumers.
- The implementation is generally fair--you can still cancel, for a modest fee.
- There are also good consumer work-arounds. E.g., book fully-refundable well in advance. Then, when within a few days of your travel date, and you are confident things won't change, cancel that and book a pre-paid.
So bottom-line, this has a lot to recommend it, and there aren't any really nasty gotchas. Also, I think the prepaid option will pretty much eliminate any benefit to booking through the "opaque" sites, such as Hotwire and Priceline, because it will offer comparable savings with fewer restrictions and full transparency.
 Some companies far more fair than others. As of 01/27/14, Hertz is $50 for >24 hours, $100 for <24 a="" but="" completely="" hours.="" href="http://www.budget.com/budgetWeb/html/en/deals/prepayfaq.html#How do I cancel my prepaid rental PRIOR TO SCHEDULED PICK-UP TIME?" not="" outrageous="" pretty="" steep.="">Budget24>