As of the final Drupalcon Paris code sprint, http://groups.drupal.org was upgraded to Drupal 6, and its site search has also started running on Apache Solr. Since last summer we have used a scrubbed groups.drupal.org database dump which we updated to Drupal 6.x as a test set for Apache Solr Search Integration functionality and screen shots. Having it live on the groups site is great because we've been able to see for months the kind of improved search results that are possible, but frustratingly unable until now to access them in real life.
The groups.drupal.org upgrade was only one of the exciting developments, lively BoFs, or informative presentations around the integration of Apache Solr with Drupal last week. I enjoyed hearing Mike O'Conner's talk about his efforts to integrate Solr search with Ubercart, and several teams discussed their plans to use Apache Solr for existing sites or upcoming projects.