If you want to have consistency in a distributed system you need something like ZK. If ES does not have ZK it surely has something else, probably with different trade offs.
Our 2.x cluster is much more stable than our 5.1.2 cluster despite the fact that our 5.x cluster is significantly smaller (in node count) than it's older brother.
Also of note: Amazon's documentation on HTTP limits is wrong. There are some instance types listed as having a 100mb max payload that are only 10mb. We found that out when Logstash recorded a crapload of errors with the 10mb limit on what was allegedly a 100mb instance type.
Such as disallowing configuration they do not like, having memory/resource leaks that they cannot find the root cause for and few other things I forgot already. G1GC is disallowed because they had a data corruption bug with it. This is few months back, they might changed some it already. The question for me is what do I get using ES over Solr? If Solr's features are enough for our use cases should I even try ES?
It depends on your use case. If you are already familiar with Solr and it is good enough for your use case, then use it. Solr and ES are about the same feature-wise. Scaling is easier for ES because it is built-in. Here is a good comparison of their APIs.
