Zug? So it's (damage+critical)*2 not damage+(critical*2). Geez, sneak attacks are even more insane than I had previously misunderstood.
Then add in headshots on top of that.[I believe its an extra 50% in most cases]
Most video games don't really reward stealth and careful aiming for the head that much, its usually pointless unless its a forced requirement for the mission. But fallout greatly rewards being a stealthy, accurate killer.
How fun is being the stealth assassin when any foe takes at least two shots and there is no way to say hidden after the first shot? its not fun at all. On the other hand how fun is it when you constantly have to be stealthy and aren't allowed to make a stand up fight. Fallout gives us the choice of how we slaughter our enemies a knock-down brawl is probably faster but more hazardous.
While the stealthy route is slower but safer.
But really the damage multipliers in Fallout 3&Vegas are nothing compared to the insane things you could do in Fallout 1&2.