Hopefully some reassurance for those of us still awaiting our tickets; I had a fax from the ACO today requesting 13 euros to finalise my booking as the EXPO parking I had been on the 'wait list' for was now available (the other components of my booking were paid for two months ago).
When I gave them a ring, a very helpful lady took my credit card details over the phone (only in exceptional circumstances she said) and assured me that I will receive my tickets via UPS next week.
So if you're still waiting, they're obviously still despatching!