So you are saying a shield's speed rating effects movement speed, and not the speed of shield raising/lowering? Or does it do both?
Shieldskill doesn't have anything to do with your movement speed. At all. The main problem here is the sheer weight of the slower shields. The weight of your weapons/shields does not contribute to any wpf penalties, but it does affect your movement speed.
For instance the steel shield: weight 12,5 and 61 speedrating.
Compare it to the steel buckler: weight 3,5 and 98 speedrating.
The steel shield will slow you down a lot, while the buckler will hardly have any effect.
Shieldskill increases coverage (forcefield), reduces damage taken by the shield and supposedly has an effect on your feintspeed (I hardly notice any difference between 5 or 6 though).