At the moment, I only have two WordPress sites for which I have shell access, so WP-CLI shouldn't be a big deal for me. But it is.
The whole idea of managing WordPress.org sites in the console (and being able to avoid the WP Dashboard) is such genius, I wonder why nobody thought of it before now.
The possibilities, especially when WP-CLI is combined with traditional shell scripting, are many. From updating the software, installing and managing plugins, this drags WordPress into a realm where sysadmins can really get things done and save a lot of time doing it.