Installed and all working perfectly. When I saw your screenshot showing the updated kernel I knew I had to root. I have the Z3 and the same 17th Sept kernel (obviously not the 'same' but I guess it's the date Sony gave there devs)
Thing is here in Ireland things worked backwards; With my Z3 6603 I received the first update a few weeks ago with the new kernel, then I got the stagefright fix. With the Z2 tab it's different; got an update few weeks ago (2-3) with no stagefright fix or 'recent' kernel. Then stagefright is released in past few days ( 2-3) but also included is new kernel. Maybe I am over thinking.
Bottom line is the Sept Kernel is way better... Perform and batt life.
But cant figure out Sony... I think if you don't have their latest flagship then they will provide you with software but just out of necessity ( granted improvements). They just have too many products ( low, ultra low, Mid, regular, premium..) Why can't they just produce one/two good phones and maybe a tab or pro tab every and focus on that