Mine after update..no problem.
Am not into networking so dont know bout wechat or tango.
But candy crush played just fine.
Battery not very sure as i found quite the same as on 4.1.2 but right now am working outstation for two days already and i leave my Note 8.0 inside my drawer. Don't know how long the battery will last if left untouch...lolz
Just hope the battery won't dry up till kaput.

Will be back tomorrow and see how it goes...

Glad to hear that 
Mine on 3G but shouldn't use that much juice by leaving it idle.

Hmm..did you do any factory reset after update..?
I always do factory reset right after any updates coz it usually make things smoother. .less problem as all the redownloaded apps get optimize with the new firmware.

No need custom kernel if you wanna root your phablet.
If you already on 4.2.2 then you can use CF-Auto root.
If you still on 4.1.2 then you can use framaroot where the app do the one click root for you.

I use framaroot when I'm on 4.1.2. Don't know whether framaroot can be use on 4.2.2 or not.
You can give it a try and see..