The update did take a long time. Initially update to build 101514 & 101536.1000.
This alone take 2-3 hours. After complete only I notice need to update one more time to 101536.1004.
This is shorter, less than 1 hour.

Btw did any of you notice lag between screen wakes up and the time the passcode pin menu pop ups?
If the passcode are not required, don;t have this issue (I set mine to lock every 30 min)

Another one is the lock screen quick status seems to reset every time. Only phone and sms remains while the others (user set whatsapps etc) gone.
I'm currently using 640 XL.

I rolled back to 8.1 recently. Found the latest update 101536 to be more buggy than before. Main problem is battery drain. Seems this is different on each model. Using 640XL.

Hopefully the final version will iron out these issuea. As of now, I'm happy with the smoothness 8.1 offers.