As part of a recent client project at PingV, we needed to develop a method to display search pages with predefined filters that would display results instantly, without the need to enter a query – and without limiting the end users from further filtering the results on their own. Currently, Apache Solr doesn’t provide this level of customization, so it was necessary to build a custom implementation. I decided to use the Search API page module as a starting point and borrowed heavily from that implementation, removing Search API-specific functionality and adding in the ability to use filters.
You can find the result of that effort here: http://drupal.org/project/apachesolr_page
Obviously, more needs to be done to make this as powerful and flexible as it needs to be for widespread use; but I feel it has great potential, and wanted to share it here to gain input on the concept and how best to apply it going forward. Feel free to comment with your thoughts and suggestions.