This is a very handy plugin. For those who don't regularly think about making their external links open in new windows, so as to keep people from leaving a site, this is a great plugin to save some traffic for the less technical! :)
One suggestion would be for links whose URLs contain /wp-admin/ to open in a new window/tab. Of course, this would be for only those who are logged in. When you're in the WP back-end, links would NOT open in new windows/tabs.
Of course, this suggestion could be a plugin option. If someone doesn't like this, they can turn it off.
Please let me know what you think.