Thanks for your conformation. I should have mentioned that one of Craig's speculations for optimum accuracy is to set the timer interupt to high priority, and all others to low priority. The timer always interupts, but is never interupted. I can see where doing this might be a problem in many applications.

Im assumming the reason for basing the timer on 65536 is because the timer will always overflow to zero (no matter what interupt is currently in progress), so that other interupts wont disrupt the timing.