I was out of town recently, and required the use of a rental car. There are many aspects of the car rental experience I detest, mostly probably because it's about upselling on a variety of options including additional car insurance, GPS devices, and re-fueling options.
My credit cards have always assured me that one of the many benefits of carrying their card was not having to fork over extra insurance when renting a car. With some amount of anxiety, I'd initial all those spaces on the rental form acknowledging that I was refusing their extra insurance and hope that Chase (or whichever issuing bank was) meant it.
So one time the rental car agency accused me of scratching their car (which I'm rather sure I did not do, considering the extent of the damage). But we picked up the car in the dark of night and thus did not do the pre-departure check. That was our negligence, and you can be sure that I have never done that again.
So I turned to my trusty credit card company and called in their rental-car-damage chit, and it worked out exactly as advertised. I may have filled out a form or two, but the bulk of the interactions were between my credit card company and the rental company to pay for the damage. I didn't pay a cent.
So if you're wondering if your credit card company will really pay for your rental car damages, I can say that Chase Bank worked out for me. And, always, always:
Check the physical condition of the car before leaving the lot.
I usually refuse the GPS device, simply because maps.google.com does such a great job already, but I guess that's just personal preference. Also, I hear that GPS devices are much more effective in cities, but quite ineffective when it comes to small towns with their irregularities and one-way roads.
As for the refueling options, the rental companies really do price gouge on the refueling price, but sometimes it is worth the hassle of finding a nearby gas station. Also factor in that gas stations near airports price gouge, too (though not nearly as much as the rental agencies).
For me, it depends on the specifics of the flight and size of the city. On my recent trip to a tiny city I'd never been to, we'd be driving into the airport from an hour away to catch a 6:45am flight, and I didn't want to risk having to find a gas station that was open at such an early hour. So I took the price hit.
Just remember that rental car companies are in the business of separating you from your money. If you have a credit card that will cover you for rental car damages, it's a nice benefit. GPS devices may be helpful in some cases. Ditto regarding the refueling options.