This was probably much more important announcement for AAdvantage customers than Etihad Guest members (imo Etihad has a better route network, better planes, better hard/soft product), but from today you can earn and redeem Etihad Guest Miles on American Airlines' flights:
American Airlines Redemption Table
I'm wondering if we can book American Codeshare flights like SYD-LAX. From the table a first class ticket on AA 7365/AA7364 (operated by Qantas), it would cost 145,000 Etihad Guest Miles, which is a bargain!
EDIT: Just found the rules:
• The values in the redemption table are for one way journeys only. The value for return journeys will be double of the one way value.
• Flight rewards are subject to capacity control which may limit the number of seats available for award travel.
• Miles can be redeemed for all American Airlines, American Eagle and American Connection operated and marketed flights. Both Domestic and International flights are eligible for redemption.
• A minimum of 14 days advance notice is required for a making a reward flight booking.
• Reward tickets can be booked for one way or return journeys.
• A reward ticket for a child will be charged at the same mileage value as for an adult and a reward ticket for an Infant will be at 10% of the adult value.
• Applicable taxes and surcharges will have to be paid at the time of ticket issuance.
• Reward tickets are non refundable.
• Reward tickets are valid for a maximum period of one year from the original date of issue.
• Date changes are possible free of charge within validity and subject to availability.
I assume flights marketed by American Airlines include codeshare flights!