It was mass produced, standardised and issued to assault engineers and some other combat troops. Used in combat. It was not some experimental stuff. I really don't know how else can you define "practical". There are other examples of WWII combat armour:
http://www.armchairgeneral.com/forums/showthread.php?t=61956
http://en.wikipedia.org/wiki/Ballistic_vest#World_War_II
If you are trying to refute me, then you need to pick different articles:
From the article you posted
Early in 1944, as a result of growing indifference on the part of military theatres and army commanders together with the very small demands placed by them for these suits of armour, the initial order for half a million sets was reduced to 300,000 sets, of which some 79,000 only were issued, 65,000 to the RAF and 15,000 to the Army in all theatres, the majority going to the 21st Army Group where the major portion was allocated to the Airborne Divison. (2) The Army in Italy had no requirments except for some 300 sets for Royal Engineers personnel on special duties. The remaining stocks were held in War Office depots and were never issued.From the other article you posted
In the early stages of World War II, the United States designed body armor for infantrymen, but most models were too heavy and mobility-restricting to be useful in the field and incompatible with existing required equipment. The military diverted its research efforts to developing flak jackets for aircraft crews. These jackets were made of nylon fabric and capable of stopping flak and shrapnel, but were not designed to stop bullets.Out of the 10's of Millions of Soldiers fighting on the Allied side, I would hardly call 15,000 sets of body armor prevelant or common. Or, even Mass Produced when compared to the quantities of uniforms, shoes, belts and other kit that was typically given to soldiers. Body Armor was availible to about .075% of the troops. Now, Flak Jackets were quite common, but that was for air crews and pilots where individual mobility was not a concern.
At best, you can call Body Armor in WWII a failed experiment. There was no widespread use, and even when issued in the very limited amounts it was, most soldiers would not use it as it slowed them down to much and it did not offer much protection.
It was only during the Vietnam War that Body Armor became practical and it's use started being more common.