I have read many reviews on the Dollar (and other) listings, one common issue I cee is that customers booked thru a third party site, although often easy to do when booking flights, hotels, etc... one is much better served when booking and reading conditions directly from the site owned and controlled by the rental company. Example - on way rental if booked correctly on the site your reservation is processed to the counter correctly (and confirmed in an email - which you should take with you). Example - third party 'insurance' - if you buy 'insurance' on line (Orbitz) you are NOT buying the coverage offered at the counter by the rental comany -- BEWARE of the online 'insurance' offerings. The rental car companies are in the business to rent cars and make money, they want you back - if you have a problem start with local manager, act calm (screaming does not help), and give the facts - don't fluff up the story to sound worse than it really was, and make a suggestion to solve the issue.
I am in a rental car every week, and by far Dollar does the best job (on average) accross the country