I doubt this will be controversial, but I figured someone should ask what the community consensus would now be. :)
Our current position on wp-cli is probably well summed up in this post by Rarst:
While WP CLI is not explicitly on topic, we tend to allow questions about it because of it's unique role as related to WP project and infrastructure.
However, Matt Mullenweg has today announced that wp-cli is now part of WordPress.org:
The website of wp-cli.org, the code / GitHub, Twitter, and such are all coming in under the WordPress.org umbrella
Of note, a recent questioner ran into some problems when asking about wp-cli, and we've previously had confusion about the disambiguation between Automattic and WordPress.org, so I thought it would be a good idea to get a clear answer on where wp-cli now stands so we can point people to this in future.
So the question is: is wp-cli now on-topic for WPSE?