They have a variety of companies. I just use Alamo, because I have always had a good experience with them. When you go to the AAdvantage site you will see the points listed relatively high because it logs you off for some reason when you are browsing the car rental portal. Be sure to take the next step in the dummy booking (may require a re-login) and the points drop in half.
One thing also is to be sure your trip is firm. You can switch dates for a $30 fee, but not locations. That will cost you $150, so be sure your location is firm.
Just did the AA Aviator card for a single purchase and a $95 dollar annual fee (and I hate AFs as much as South Fayette Fan!), but will I pay $95 for potentially $2,000 plus in free car rentals? Heck yeah! We have used in LA, Orlando, Richmond, Philly, Vegas, Dallas, etc. with no problem. We are SW flyers exclusive, so it has been a great way to use AA points.