I really disliked it.
Rikka's problem is just rehashed stuff from S2(Muh losing imaginary powers) and she's also less cute now that she's grown up and still acting retarded. The Deko/Nibu arc feels like forced, unfunny comedy skits, The ending didn't really resolve anything and the kiss they had built up to for two fucking seasons and one entire movie wasn't even shown in closeup.
Rikka being too retarded for college makes sense but her sister taking her to Italy makes none. Seriously, she doesn't know one word of Italian or English, she obviously won't be going to college there so why wouldn't she stay in Japan to do the lifetime of pleb work in front of her? Besides, her mom is off in Hokkaido anyway so why does her mom going off to Italy mean Rikka has to go off too? Her living situation doesn't change at all.