Please dont insult me (im to young to be insulted ;) ), but is the reason why this weapon is so strong is because of its stun ability? i have never used it before.

How long does stun last for, and is the berserker rage the only thing that can thwart it?

The stun is it's biggest asset. Additionally, you get a 5% chance of 20 points of electric damage and 1d10+3 is about as strong as it gets for a one handed weapon (except for crom) in SoA.