The stopping power, IMO, should slow you down to walking speed (which is what I think is does from the vids I've watched), nothing less because you're still in the Sprinting animation, there's no reason to make you even slower than walking speed when you can't shoot.
It's really all about personal taste obviously, but in a game with fast kill times it's not much of a problem. Imagine CoD without Sprint? Sprint in Halo Reach was flawed because the killtimes were too long, no bleedthrough, no slowdown, etc., but hopefully Halo 4 doesn't have that consistent problem when you couple the improvements of faster kill times and the slowdown mechanic.