I probably rent as much as, or a bit more than, you and generally from Hertz. I'd say my upgrade success with them is about 90-95% at airport locations and 10% at downtown locations, but most of those are in NYC on weekends, where an entirely different market is in place. Although it can be very frustrating, I think Never Lost is really useful when you don't know the city. I use Avis periodically for the BA mileage bonuses or when it prices significantly cheaper, and, like one of the posters above, have not had good experience with upgrades with them, even though I am supposed to get them. At least in the NYC metro area, Hertz with the AAA discount usually prices less than Avis with any discount I have with them. I think National's Emerald program is great, and they are usually cheaper than Hertz, but they're not everywhere, and I've found it more worthwhile to consolidate my renting with Hertz, get the points and the free rental cert after 15 rentals.