TrueCrypt is not secure as it may contain unfixed security issues.
Proof? The first has yet to be "cracked" If you use it with a pass-phrase and one or more key-files!
TrueCrypt is the only one that has undergone a real security audit... Key derivation, salt and even iteration count I don't consider "security issues". The only things that are "issues" are short passwords and laziness when creating the encrypted container/volume...
I'm taking this opportunity to announce that we have been able to implement SHA-256 key derivation for system boot encryption (200 000 iterations). TrueCrypt has been always supporting only RIPEMD-160 for system partition encryption and this clearly needed an upgrade because of the aging RIPEMD-160 even if no public attack exists for it.
But I admit that VeraCrypt looks good and safe...
Personally I use AxCrypt sometimes which is provided by axantum software.
+1 for AxCrypt, very good software for encrypting individual files! It has a portable version which makes it ideal for use on USB's.
PS: If you use a pass-phrase you can unencrypt them with 7-Zip on Linux but If you use key-files it's Windows only!