Actual performance data for AAW systems is hard to come by, as we've seen. The May 2013 issue of Proceedings (p. 65) offers a bit of data for the Ballistic Missile Defense system. Proceedings reports that Aegis/SM-3 have intercepted 22 of 27 (81%) missiles in test firings.
There are two ways to interpret this information.
We should be encouraged because both Aegis and SM-3 are still developing and and 81% success rate is outstanding and will only get better as the system matures.
We should be disappointed because these test firings are highly staged affairs with perfectly tweaked missiles and radar systems launched under absolutely ideal conditions against extremely simple targets in a non-ECM environment. A failure rate of 19% doesn't bode well for actual combat situations against high performance ballistic missiles with on-board ECM.
Where does the truth lie? Somewhere in between, undoubtedly. Both perspectives are true although I lean far more towards the latter. The Navy is famous for staging test firings which are ridiculously slanted towards success. Nonetheless, the data offers a hint that China's carrier-killer missiles that so many people are so terrified of won't be quite the wonder weapons that they're made out to be. Aegis/Standard is capable of some level of BMD success.
Although I've stated it many times, it bears repeating that China (and the US) have not solved the far-over-the-horizon targeting challenge. That weakness combined with some level of BMD intercept capability suggests that ballistic missiles are no more than a low level threat for the time being - a threat to be respected, for sure, but not a game changer, yet.