If you get the SP4, and have a 64GB SDXC microSD, please check and see if it can use it. It seems the Surface Pro 2 and 3 models, people reported that it will either loose the ability to read the card or fails to even see it. I tried it on my SP2 and It will work. But after a few minutes, the drive letter will change from "stuff:" to "SDXC:" and now will not read the card. You have to eject it for it to find it. Or when turning on the computer, it won't even find the card (no drive letter) until I eject it and put it in a few times. I hope the new SP4 doesn't have that problem. I couldn't test it in the store's computer. You know, not being a "secure" thing to allow.