I am using it myself. My specialty is application performance monitoring, but when I'm putting systems monitoring in place for the backend, Grafana is the best solution for views and dashboards.
I have utilized Grafana's integration capabilities with Prometheus. In a previous role, we displayed some data with Elasticsearch. I have used it heavily with Zabbix integration as well. I have done Nagios in the past. It depends on the toolset that the customer has, but Grafana is very appealing because the business appreciates the views that come out of Grafana as it gives them the views they want.
I have employed real-time metric visualization capabilities. That's basically what monitoring is - a real-time view. I build up these dashboards or real-time views, but they can also be used as historical views, pulling out more data.
Grafana's role-based access control and multi-tenancy features are important for my organization. At the moment, most of our Grafana is on-premises, but we're looking at cloud options as well. Multi-tenancy is quite important because we have customers that will only want to see their information and not any other. They're not allowed to see some of the other data that we collect, so it's important to have a multi-tenant system.