Have not and will not try 6.5.30 as am using only xiaomi.eu ROMS and from what I know they won't be releasing 6.5.30 for mi5.
It seems I will stay with 6.5.19 since with the apps I am using I experience zero bugs + it has great battery life.
I am also testing latest alpha versions in parallel which are all great battery life performers, but there are few things I dislike about - (1) notification shade is ugly IMO and so are other areas within the phone that have been re-painted (miui 7 transparent/aero like theme is much better looking); (2) With "Skip lock screen" ON Floatify app does not work fully - meaning floatify notifications are hidden when unlocking the screen; (3) there aren't any new features or improvements that I care for 2 much to switch just yet