Thanks, everyone, for all the advice.

As it turns out, shockingly, I didn't have to go through a scanner at RDU. I wound up in the far right lane (Terminal 2 checkpoint), and the MMW was blocked off. Three people ahead of me, they unblocked it, but the MMW's so much slower that the TSO in front of it just waved me through the adjacent WTMD. TSOs at RDU were surly and barely communicative, but not downright hostile...perhaps that's because I never had the chance or the need to opt out.

Next flight is through MSY, so we'll see about that one...