I've found that Avis has the most consistent and highest average level of customer service out there. True, the cars of the GM line are not tops, but you also roll the dice with other companies. They will usually give you your pick of cars if you ask the agent waiting for you at the bus. It takes a few minutes for them to swap you. I belive you can also add some hints to your profile such as "no malibus". Its not guaranteed, but most locations seem pretty willing to please.

I've tried the Hertz thing, but their customer service has become horrible, and their cars below full size seem to usually suck. If you can rent from the Prestige Collection, Hertz is tops, for the rest of us? Not me as least.