AnnaS:
I too have had good experience with Budget, although, just as a walk up. I chose National because I still get 500 CP miles per rental (1000 for a week or more), and they are usually posted within 24 hours of the rental.
National also lets you pick your own car, but there are few class restrictions. You can walk up and take any vehicle on the lot. (Exceptions are mini-vans, 4x4s, and luxury cars, although, from time to time, I'll find one of these in the Emerald Aisle area. I recently got a "loaded" Ford Explorer in snowy eastern Canada, for $32 Canadian, per day.

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[This message has been edited by KenHamer (edited 03-03-99).]