Comparing page source of the main Thesis admin page with and without S:P activated (I can provide you with the full page source of both if needed), some differences I see are:
In the head:
<link rel='stylesheet' id='spMenuStyle-css' href='http://test.prometheus-unbound.org/wp-content/plugins/simple-press/admin/resources/css/spa-menu.css?ver=3.4.2' type='text/css' media='all' />
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-content/themes/thesis/lib/js/menu.js?ver=3.4.2'></script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-includes/js/jquery/jquery.js?ver=1.7.2'></script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-admin/js/utils.js?ver=3.4.2'></script>
The S:P stylesheet and jquery.js?ver=1.7.2 are loaded only when the S:P plugin is activated.
In/after the footer, this is without S:P activated:
<script type='text/javascript'>
/* <![CDATA[ */
var commonL10n = {"warnDelete":"You are about to permanently delete the selected items.n 'Cancel' to stop, 'OK' to delete."};/* ]]> */
</script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-admin/load-scripts.php?c=1&load=admin-bar,hoverIntent,common,jquery-color&ver=3.4.2'></script>
And this is with S:P activated:
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-includes/js/admin-bar.js?ver=3.4.2'></script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-includes/js/problem-with-post-edit-buttonoverIntent.js?ver=r6'></script>
<script type='text/javascript'>
/* <![CDATA[ */
var commonL10n = {"warnDelete":"You are about to permanently delete the selected items.n 'Cancel' to stop, 'OK' to delete."};
/* ]]> */
</script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-admin/js/common.js?ver=3.4.2'></script>
<script type='text/javascript' src='http://test.prometheus-unbound.org/wp-includes/js/jquery/jquery.color.js?ver=2.0-4561m'></script>
I hope this helps.