Hi, I love your plugin but I believe I found a bug with the latest version.
When making an AJAX request in WordPress ( following the method recommended in the codex at http://codex.wordpress.org/AJAX_in_Plugins ) as a logged out user I'm seeing PHP warnings in the output.
Warning: array_merge(): Argument #2 is not an array in /Applications/MAMP/htdocs/gm-newsroom/wp-content/plugins/codepress-admin-columns/classes/storage_model/post.php on line 97
Warning: array_filter() expects parameter 1 to be array, null given in /Applications/MAMP/htdocs/gm-newsroom/wp-content/plugins/codepress-admin-columns/classes/storage_model/post.php on line 97
Warning: Invalid argument supplied for foreach() in /Applications/MAMP/htdocs/gm-newsroom/wp-content/plugins/codepress-admin-columns/classes/storage_model.php on line 290
I believe this is because you are initializing the plugin in the admin and performing queries that assume the user is logged in. However during an AJAX request is_admin always returns true ( even on the front end ) but the user may not logged in. I could be wrong about that - just my two cents.
I've applied a temporary patch which works for my needs but may have some unintended consequences that I am not aware of.
if( defined('DOING_AJAX') && DOING_AJAX ) return false;
I've placed this at the top of the init method in your main plugin file.