There was a banner ad on the Citi site yesterday that mentioned some perk for signing up for AAdvantage dining and using your Citi AAdvantage credit card. I'll have to go to the site and see if it's still there for the details. I'll edit when I do.

Edit: The perk is that you get an additional 500 mile new member bonus (in addition to the current 1500 mile bonus) when you sign up and register your citi aadvantage card:

**Exclusively for CitiŽ / AAdvantageŽ cardmembers, earn a total of 2,000 bonus miles when you enroll in the AAdvantage DiningSM program for the first time between 7/1/09 and 8/31/09 with your CitiŽ / AAdvantageŽ credit card and dine within 30 days of joining (minimum spend of $25). 1,500 AAdvantage(R) bonus miles will be awarded by AAdvantage Dining in accordance with terms above. The additional 500 bonus miles will be awarded separately by the American Airlines AAdvantageŽ program 6-8 weeks after qualifying dine.