Yeah the change in how apps can access the SD card seems to be the biggest change. I am not really affected by that because I don't use my as card that much. Just for photos and songs.
I have KitKat on my g pad gpe and my nexus 7 and I love it. Particularly with the vanilla ui. Now, my biggest reason for using the Hyperdrive ROM is to get the aosp lock screen and change the colors of the UI to be cleaner and look more vanilla. I am so excited for KitKat that I was considering upgrading to the official, then when root comes out for it use Wanam Exposed to change the quick settings colors and what not. One they update the S4 to the new S5 interface I won't need the color change stuff because from the pictures it looks much more tolerable.
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