Locate your client_settings.ini.

It's located in C:\Users\User_name\App Data\Local\SWTOR\swtor\settings.

Add this line to the section titled [Renderer]

"AntiAliasingLevel = 4"

Profit! You can of course replace 4 with your preferred AA number.

Make sure you get the right folder. You can safely delete the betaclient folder, that's no longer used.

And enjoy SWTOR in the less than jaggy goodness.

Disclaimer: Settings were tested using an NVIDIA card, i've heard reports it does weird and wonderful things with ATI cards, mostly due to the way that AMD processes shadows, since it uses UT3's shadow mapping.