I find Redis is very useful when you need fast, temporary access to memory in a distributed system. I have used it several times as a distributed lock, or as storage for real-time computations in a distributed system that only use primitive values, for example aggregating page views into different clusters (hashes or sets in Redis) and then saving the result to DB.
Kleppman is the author of Designing Data-Intensive Applications and generally someone whose opinion I trust in such things.
I love Redis and use it extensively at $dayjob, but I stick to Consul for managing distributed locks. Consul was built from the ground up to handle such things; Redis handles it as a bit more of an afterthought / consequence of other features.
