Your shield raises more slowly if you're running, but they still all raise at the same speed. Also, your shield doesn't need to be up to block arrows. It only needs to be facing the archer. That's why when I run past archers I run with them on my left. Their arrows almost always hit my shield.
It's because of this "almost" that i like to raise my shield. Who cares about 1 extra second running time, when you can be headshotted. Depends of the archer, ofc, but all these shielders thinking the shield on their side will still stop arrows thanks to forcefield are really taking risks.
What is funny though, is how forcefield (wich is suppose to represent the shielders awareness, to move a bit his shield in the right direction) still works on cav who have just been dismounted. Awesome shield.^^
Back to topic, they raise at the same speed, alright, but that's because it's the same animation. What i'm speaking about is a sort of delay of "im protected" AFTER the shield animation is finished, or in process. And that depends on the shield skill.
Anyway, as an archer or shielder, i'll be delighted to help see what this shield speed is, in a duel server or whatever. It really doesn't seem that important if rustyspoon is right. :S