Effective range is more a personal limitation then it is a carved-in-stone rule. If you wanted a ball park number i would imagine most people would say between 30-40 yards though. There are many people who can, and do, shoot deer farther then that but personally i think you start pushing your luck when you are shooting past 40 yards.

If you've watched many hunting shows or talked to many bow hunters i'm sure you've heard about deer "ducking" arrows. Well when you are shooting from 50 yards, no matter how fast your bow is, it takes a while to get to the target. This is more then enough time for a whitetail to move or duck causing a bad hit. Some of the other species (elk, moose, mule deer etc) do not seem to jump the string as much as whitetail and they are generally larger targets so i would feel more comfortable shooting from farther away. But on those shifty little whitetail i think you would be better off trying to limit any long shots.