My multisite installation dropped from speedrank 87/100 to 70/100 with this plugin. As recommended, I had wp-content and wp-includes redirected to a completely different domain (not subdomain) on the same server.
Well, Google Page Speed’s wish to have static resources loaded from a cookieless domain worked. But the unparallelized request completely killed my rather good speedrank.
Until further illumination I rather get back to define my CDN with functions.php