With the development version of the plugin (0.8-alpha), you have a ‘p2p_orderby’ query var, which you can use with WP_Query, like so:
$my_query = new WP_Query( array(
'connected_to' => get_queried_object_id(),
'p2p_orderby' => 'my_connection_field'
) );
More info on connection fields:
https://github.com/scribu/wp-posts-to-posts/wiki/Connection-information
Note that this is alpha software and you still have some work to do on your own.