I shot a mule deer two years ago with my SKS. I used a hunting round rather than the surplus ammo most people associate with the gun. The shot was only about 70 yards and the buck feel in its tracks (one shot, as Boo says, is all that's needed). As long as you can shoot the thing accurately, I don't see a problem with it (it shoots as good as my 30-30). I doubt I'll use it again, but one never knows.
I know there are people out there that poo poo the idea, but to each their own.