I wear one and I love it , you will get the added occasional bounce that you maybe wouldn't of got otherwise , but they are available for everybody ,and too rule against them would be pretty stupid I think plus maybe not the brightest market research from Proto (although you could still train with it I suppose, but what would be the point).They do add a level of protection which is appreciated and the idea that we should not wear things that stop us getting hurt more is patently ridiculous. I know we have to have sensible limits so no Mitchellin men on the feild but i think these fall in to an acceptable level.
Plus you get to look like Batman ...