Emergency services, particularly in rural areas consider it a godsend and have spent big money on licences. Personally speaking it’s fairly pointless beyond being amused about your own front door words.
Just to clarify; we are not charging UK emergency services to use what3words. Here is a list of the 87 services using what3words https://what3words.com/news/emergency/uk-emergency-services-rollout-what3words-in-control-rooms-to-save-resources-time-and-lives/ …