Phoronix frequently include Nexuiz benchmarks in their reviews. With the image quality tools that are now being included in the Phoronix Test Suite, they have now doen an article on the effects on performance and image quality of different AA settings:
http://www.phoronix.com/scan.php?page=a ... nvik&num=1

Can't say I'd bother with AA based on the performance impact and marginal image quality.