This is actually an answer to a question about this plugin that I solved on my own and I think that it would be a good idea to share the info.
To reverse the order of the posts in the admin part, modify these lines in postMash.php (postmash-filtered v.1.2.1) to:
$query_post .= " AND $wpdb->posts.post_type = 'post' ORDER BY menu_order ASC ";
$query_post .= " ORDER BY menu_order ASC " ;}
(Add ASC in the end of the query string)
Now you will have the newest posts on top and the oldest ones down the bottom. This can be quite handy if your posts has this order on your site.
Thanks for a GREAT plugin!