In 27 years, I've used them twice, if that. I will eventually use one in Ptolus if/when my campaign gets involved in the Banewarrens and the Pactlords of the Quaan. Otherwise, I see little reason to use them. Used more than sparingly, they're way too over the top for me.
That said, a rerelease of the monster module series from 2E would get me to consider it. The mind flayer one had them trying to black out the sun, yes?