In the Kibana upgrade, we lost several important features, which overall make the logstash / kibana infrastructure significantly less useful for tasks like investigating ongoing issues or anomalies.
The previous version of Kibana offered a histogram of values for a given log property in a query. We used this extensively for tasks like finding top user agents sending specific requests, getting an idea of response code distribution, looking for failing pages, and so on.
Furthermore, the histogram tool supported adding further criteria to the current query by selecting values, which made it very useful for quickly drilling down into the data.
We were also able to select the log type/level and fliter based on that, which was extremely useful.