Cryptographers Alex Biryukov and Dmitry Khovratovich has recently published a paper called "Related-key Cryptanalysis of the Full AES-192 and AES-256". In this paper they present two new related-key attacks on the full AES that are better than brute force with a complexity of 2^119.

Here is the abstract:
Abstract. In this paper we present two related-key attacks on the full
AES. For AES-256 we show the rst key recovery attack that works
for all the keys and has complexity 2^119, while the recent attack by
Biryukov-Khovratovich-Nikolic works for a weak key class and has higher
complexity. The second attack is the rst cryptanalysis of the full AES-
192. Both our attacks are boomerang attacks, which are based on the
recent idea of finding local collisions in block ciphers and enhanced with
the boomerang switching techniques to gain free rounds in the middle.

Bruce Schneier has something to say about it here in his blog.