stats.jsp is cool and all, but suffers from escaping issues, and also is not accessible from SolrJ or other standard Solr APIs.
Here's a request handler that emits everything stats.jsp does.
For now, it needs to be registered in solrconfig.xml like this:
<requestHandler name="/admin/stats" class="solr.SystemStatsRequestHandler" />
But will register this in AdminHandlers automatically before committing.