I've found Discover to also be extraordinarly protective of their customers. I can dispute anything and the charge will be wiped away immediately. I've never waited even a minute to talk to a CSR. If my purchases go even slightly out of whatever they deem "ordinary" I get a call within 5 minutes. My bank and some of my other cards do the same, but it takes them as much as 2 days to get around to calling. Best creditor I've ever had, although I have no complaints about AMEX either.
On the subject of rental cars I think Avis might well have you beat. I rent frequently and I've tried them all numerous times. But Avis screws something up about 25% of the time. I've been charged for renting cars in places I've never even been to. The latest screw-up was them charging for $1200 per day to rent a Crown Victoria. But the worst part was when they tried to say I authorized it because I requested an upgrade at the counter (I usually get them for free or for a very negligible amount if they have something available).
