In my mini 2, the performance is definitely better, no placebo there.
For example, in Safari's favorites page, landscape mode, it would lag like crap when tapping on the history/bookmarks pane.
Now on iOS 9.3.3b2 it's practically gone.
However, there's still some lag(sub-25fps) when opening the home card on AppSwitcher.
Otherwise for the most part it's fine.. Until iOS 10 invariably screws it over again
Oh! And speaking of long standing bugs, there's still no animation in messages when you hit Edit then Done. They just snap back!