I agree, and I don't get where the claims that ES is hard to operate originate from. Yeah, if you allow arbitrary aggregations that exceed the heap space, or if you allow expensive queries that effectively iterate over everything you're gonna have a bad time. But apart from those, as long as you understand your data model, your searches and how data is indexed, ES is absolutely rock-solid, scales and performs like a beast. We run a 35-node cluster with ~ 240TB of disk, 4.5TB of RAM, and about 100TB of documents and are able to serve hundreds of queries. The whole thing does not require any maintenance apart from replacing nodes that failed from unrelated causes (hardware, hosting). Version upgrades are smooth as well.
The only bigger issue we had was when we initially added 10 nodes to double the initial capacity of the cluster. Performance tanked as a result, and it took us about half a day until we finally figured out that the new nodes were using dmraid (Linux RAID0) and as a result the block devices had a really high default read-ahead value (8192) compared to the existing nodes, which resulted in heavy read amplification. The ES manual specifically documents this, but since we hadn't run into this issue ourselves it took us a while to realise what was at fault.
The only bigger issue we had was when we initially added 10 nodes to double the initial capacity of the cluster. Performance tanked as a result, and it took us about half a day until we finally figured out that the new nodes were using dmraid (Linux RAID0) and as a result the block devices had a really high default read-ahead value (8192) compared to the existing nodes, which resulted in heavy read amplification. The ES manual specifically documents this, but since we hadn't run into this issue ourselves it took us a while to realise what was at fault.