The memory card is very fast. With the Transcend USB 3 card reader which is benenen 90 MB / s are nearly achieved. The card in the camera (OM-D E-M10) is also not a "bottleneck" and everything always responds quickly. The problem I see, however, that the camera has now been several times of "Card Error" is displayed and made images has not been saved. With the size of 64 GB, this leaves a slightly queasy feeling.