Expect can be a lifesaver when you cannot use your usual go-to tools like Ansible etc. especially with legacy setups where you cannot tweak stuff much. I have successfully used it combined with tmux for automated multi-term like functionality, deployment verification and other chores to save a lot of $ for my company. I do try to keep my Expect scripts as simple as possible though, just so I do not have to remember too much since I do not work with TCL anywhere else.