[GeeTwo]

While I haven't tried it with Talons specifically, I have seen a definite difference between the two cases just playing with the motors not under power and shorting them out. Since the resistance is constant and the voltage generated is proportional to the rotational speed, the amount of energy dissipated should increase with the square of the rotational speed. That means it will probably be pretty good at getting the robot from full speed down to a crawl (though the motor will heat up as it absorbs the energy!) but it won't be so good at resisting a slow steady force.
I have considered using shorted-out motors as a brake to a catching device for just this reason; if we don't need all of our allowed thirty pounds of manufactured parts for spares, we may look at this as a post-stop-build project.