As Adrienne said, I've used Carjet a lot to book a car. They are brokers, and I have always wound up

When I was going to Portugal, tour of rome italy Laurie Reynolds (poster who has lived in Portugal), recommended Car Jet. I didn't use them because I wanted to pickup in Evora and they did not have a facility there. But their prices were better than AutoEurope's.
As Adrienne said, I've used Carjet a lot to book a car. They are brokers, and I have always wound up with Budget/Castanheira, which gives quite good service (you can do in-town tour of rome italy pick-up and airport drop-off, and vice versa for example).
I remember once that i booked through Carjet and they were going to put me with some agency I had never heard of (Carjet reveals the agency right after you make a reservation, but you can always cancel if you're unhappy with the agency you get stuck with). I wrote to them and said I have never heard of this place and preferred Budget. They sent me a price that was a little higher than this unknown agency's price and I just took that.
When booking with Auto Europe, you know which agency will be supplying the car before you book the reservation. All you have to do is call AE, or check out the agencies address pickup address. It's pretty straight forward, but maybe too easy for some.