I'm here purely from my subjective feeling and because I think the speed really great. I take pictures with the Pixelmonster Nikon D800 (36MP) and as you can tell if the card stores too slow. Here I could not notice any delay.
I have photographed in October in Iceland so and under very harsh conditions. Cold and heat alternately is actually not that great for the art, but if you suddenly need the vehicle to warm up and sift want the images from the cold, you have to reckon with the resulting condensation. The camera and the card have but all survived without complain about. Only my additional SD card of another manufacturer decided to stay here at short notice: D.
A good product, I have nothing to complain about!