I don't think AES is fully supported yet.
I run 12.2(15XR) on a 1200 and trying to specify AES-CCM as a cipher and the message "Warning: interface Dot11Radio0 does not support AES-CCMP" is returned.
I believe it should be working within the next release or two: Cisco was recently listed as one of the first available WPA2 supported platforms (AES is the primary cipher).
FWIW
Scott