If you use the official update, you will get the extSDCard read/write errors back, as they are part of Kit Kat .

to fix, once rooted on the official rom, Open the platform.xml file just like in the custom Kit Kat roms and make it look like this

<permission name="android.permission.WRITE_EXTERNAL_STORAGE">
        <group gid="sdcard_r"/>
        <group gid="sdcard_rw"/>
        <group gid="media_rw"/>
That "SHOULD" fix the read/write problems. Kit Kat is made to only read and write to the internal storage to keep Android running smoothly as people sometimes by cheap laggy sdcards.
--HTC One (M*8)
--Note 10.1 2k4
-Recovery: TWRP
-Recovery: TWRP
-OS: Android 4.4.2
-OS: Android 4.4.2
-ROM: xKat V3.2
-Kernel: ?
-Kernel: Bindroid V3

Blog: MobileEscape.blogspot.com

Retired: Behold, G1, MT Fender, MT3G Slide, Vibrant, N1, HD2 (android-Froyo), Viewsonic G-Tablet, AT&T SE Xperia X10i, Samsung Galaxy Tab; HTC Inspire, HTC Sensation, Droid Charge, MYTOUCH4G , Thunderbolt, Droid DNA (traded), Note 2, HTC Rezound, Note 3 (jumped)