im not sure why people are relating the cards class to write AND read speeds. the class is only related to the write speed of the card. not the read. anyone saying they experience a more responsive phone over the class of an sd card are seeing things. and the class is merely stating the MINIMUM write speed, class 2 = minimum 2 mB/s, 4= 4 mB/s, 6= 6 mB/s and so on. these will hardly make a difference since even a class 2 can still write at speeds close to what a class 6 would write at. so most of you are paying extra money for something youll never take full advantage of.