How secure is AES-256?
I wouldn't assume that the NSA has cracked AES ciphers. I would assume that most crypto systems that use AES have implementation flaws that the NSA exploits when they feel it is worth it. 

In any case, when the only possible way a state can know something is by breaking a cipher, it's difficult for them to use that information; doing so would reveal that the cipher is broken. So in practice, a broken cipher is more likely to be used as a shortcut to find something that could be discovered (albeit with more difficulty) by other methods.



You might be interested in this recent story and commentary about NSA's crypt analytical capabilities.