We use ElasticSearch and Kibana in production for real bughunting and support requests. Logstash was too frustrating to deal with so we wrote our own simple wrapper around an open source ElasticSearch client library to log ourselves.

We log every request (everything but the body usually) and response. If an error occurs, its logged as part of the request. We can practically replay actions taken by users and easily drill down to the exact requests pertaining to an error.