Dr. Shapiro,
I have found EMDR to be a helpful addition to my work with trauma survivors. I am not particularly convinced by the accellerated information processing theory, but I read an online paper in a Traumatology journal:
(at http://rdz.stjohns.edu/trauma/contents.html )
Traumatology-Volume 1, Issue 1, May 1995. "An Orienting Reflex/External Inhibition Model of EMDR and Thought Field Therapy" by Nathan R. Denny, Ph.D.
The idea is that the eye movements elicit the orienting reflex which interferes with the fight-or-flight response and allows the brain to process the material differently.
How does this fit with your understanding?