So I bought my MBA 13" 128GB. I am thinking of using the SD card slot for extra storage. I am looking at the 64GB or 128GB cards, probably the 64 due to cost. What is the experience of those that have tried this? I am not going to use the SD storage for nothing more than documents and non intense items? By the way I am running WOW on at default and it is fine. 50-60 FPS in the default setting.