Originally Posted by
stifle
If you plan on doing a lot of travel within North America [slight simplification] and want free lounge access, you'll be wanting to get to BA Silver (oneworld Sapphire), as AA's equivalent level (Platinum) doesn't have lounge privileges on such journeys. But as Gardyloo mentions, this will require you to have four BA flights (either BA flight number or BA metal will do).
This can easily be accomplished without having to qualify for BA Silver (and probably less expensively).
You can buy an AC membership or get Platinum Amex, which for me more than pays for itself easily with its benefits ($450 annual membership) - YMMV