dallardice - Couldn't agree more. I've had the Avis/BA infinity loop a few times and it goes on for ages until you wonder if it's healthy to be so bothered about 1/20th of a European Y flight, but it's the principle. Eventually, one of them usually capitulates and applies the miles, but not always. The wheeze I hate with the smaller, far-flung or tropical locations is Avis saying - after the fact - that they are "non-automated" (whatever that means or what possible relevance to me), and that therefore no basic, bonus or voucher miles are due.
I've also had vouchers disappear from BCN, and similar problems in France. Once dropped-off very early morning in the Alps to pick up a reserved car with my snowboarding buddy, it was well below freezing, and the office was closed. We waited two hours, being repeatedly reassured by Avis central reservations that salvation was nigh, until they finally told us to take a cab for another hour to another location, where we picked up a car two groups smaller! Needless to say, that was a free rental...
On the positive side though, I usually get excellent service from Avis, particularly from my regular locations, and often drive out in something very swank after reserving something very basic. Best result so far was reserving a Fiesta from TXL - and leaving in an Audi A8 4.2!