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!