[For_Iconoclasm]

Probably. As far as anybody knows, the FBI and NSA are on the same level of cryptography technology as the rest of the world is. AES and SHA-1 are currently the national standards for encryption and secure hashing. AES is what TrueCrypt uses (as do most SSL connections and WPA/WPA2 connections).

There are some things to keep in mind though:

Fine print: As others have pointed out elsewhere in the thread, it's possible to extract encryption keys from RAM even if the computer has been (very... within several minutes) recently shut down.

More fine print: Pick a weak passphrase, and you may be shit-outta-luck. Also, brute forcing for passphrases up to a certain complexity is viable.

Tin foil hat: A conspiracy theorist may assert that the feds are far ahead of academia when it comes to cryptography, as was likely the case several decades ago (see the history of DES). I'm not sure that I believe that, because cryptography has a huge place in academia now, worldwide. It's possible, but I doubt they've broken AES.

[tptacek]

The FBI and NSA are two very, very different organizations. NSA is a feeder for software security talent in private industry. I have never even heard of someone coming out of the FBI knowing how to break into a computer. NSA people want to leave the agency to write a string of journal articles or to make a couple million bucks. FBI people want to leave the bureau to become Assistant District Attorneys. Infosec literacy in the FBI boils down to knowing how to use EnCase.

I responded to this same comment with more details that I won't repeat, but, with respect, I'd suggest not taking seriously the crypto insights of someone who equates these two agencies.

The fact that only one organization in the US Government is likely to be able to break your disk encryption isn't a moot point, because that one organization is extremely unlikely to harass a US citizen; forget the law, the simple incentives are all wrong.