A very similar situation here, although I'm running Linux on this machine and not OS X. I feel that the SED stuff (while technically true) is misleading -- I specifically chose this drive over cheaper and better drives because of this feature. Lesson learned, though.
The only thing I could ever find for Linux that supported Opal was "SecureDoc for Linux" which, apparently, is impossible to get ahold of unless you're an enterprise with a fat bank account. Fortunately, like with FileVault, dm-crypt (which also leverages AES-NI) is more than sufficient for my needs.
Thanks for the reply.