The design is good for vertical cover and (if strapped to the arm correctly) can quite easily be manoevered to meet leg attacks. It is, however, quite a heavy design, and needs a good strong arm.
It should be noted that the gent in the picture has the shield slung at his shoulder, rather than gripped for combat.
It is not known now the extant to which such 11th and 12thC shields
actually were decorated (although period fiction also gives such images), nor for sure whether any decoration was a proto-example of personal heraldry, an indication of allegiance amongst different bands fighting together, or the artistic choice of the crafters who made the shields.