Our primary use case is essentially as a visualization of system and application logs as well as metrics, and we have time-based analysis that we like to do as well. We are customers of ELK and I'm an engineer.
Kibana lets you visualize your Elasticsearch data and navigate the Elastic Stack, so you can do anything from learning why you're getting paged at 2:00 a.m. to understanding the impact rain might have on your quarterly numbers.