I agree with you wholeheartedly on the documentation, but having a full-featured HTTP ReST API from the beginning has been a powerful driver for ES, imho. Depending on your use case, this may or may not matter. Currently, I use/admin both - ES for logs, Solr for actual full-text document search.
In our use cases, where the search experience is modeled after google in terms of simplicity. There is simply no opportunity for end-user to configure a complex search criteria.
Solr has excellent documentation. The query documentation and examples could use some work, but a lot of basic functionality is quite intuitive. The pivoting engine is also really good and scalable.