> Elasticsearch mostly "just works", and we didn't have to worry about complex schema definitions, working with giant complex XML files (hello Solr)

If you were using Solr there are a few operational modes to run in. Config file based or SolrCloud[0]. The latter is more akin the ES in terms of cluster management.

I agree though from an simplicity of deployment perspective at scale ES is has a much lighter learning curve.

[0] https://cwiki.apache.org/confluence/display/solr/SolrCloud