As detailed here:
Between 2.6.5 and 2.6.6, mcrypt performance went from great to awful, as a result of now defaulting to openpgp. In addition, openpgp cannot handle large files at all. Given the massive performance and functionality problems, I feel that openpgp should not be the default for mcrypt, until those issues are resolved upstream.
I've attached a patch which simply reverts the default back to the mcrypt method, rather than the openpgp method.