I've implementing a design for Drupal 6 that was designed using 'Smooth Navigational Menu' from Dynamic Drive. It's a cascading menu design using CSS and jQuery visual effects.
http://www.dynamicdrive.com/dynamicindex1/ddsmoothmenu.htm

It's applied to the primary navigation and runs to 3 levels in some sections. It appears to run slowly and there is a concern that this may be due to the way in which the various Javascript files are called.

Does the order in which Javascript files/libraries get called have a significant impact on performance?
Has anyone ran this menu script usng Drupal? with success or not?!

(personally I don't like this menu script and prefer the CSS only approach)

Thanks in advance for any advice you can offer.
Paul.