G'day, love the plugin, hope to donate once someone donates some more to one of mine :)
I've hit an unusual problem with a website I've done some work on. They've installed Page Links To and they link some pages to PDFs. Of course, they don't want the PDFs indexed in Google.
If you were to add a filter to change the list of posts to exclude, I could add those posts to the list before you complete building your SQL for posts/pages. Something like this, at about line 1677 of sitemap-core.php:
$excludes = apply_filters('sm_excluded_posts', $excludes);
I reckon there might be a few more people who'd be very happy with that.
In the meantime, and for anyone else with a similar issue, what I did was kludge a filter hook for when this plugin loads its options, to append my excluded pages to what was stored: