I've been playing this recently and I definitely get why people like it so much. I've played this card collecting games before and never felt invested in these characters you get from the cards because outside of a picture that's it, but giving the characters their own 3D model, voice actor/actresss, backstory and side quests you go on with them really makes me even invested in the 1 star characters ha.
Gameplay is nice and addictive, I really think there is scope for SEGA making this into a full blown retail title without it being F2P and all the strings it has attached. Simple yet deep enough to hold my attention for a while. Another neat feature is you can't put in duplicate characters into your time (Unless it's a friend off the pool of players to pick from.) it's great how much thought went into this game and as I probably bang on a bit much, really think it has the base to expand into a full blown game.
I think the monetisation is pretty bad though. 1 AP every 8 minutes seems pretty bad and when SEGA's native version is I think 1 AP every 3 or 5 minutes, some of the later missions are going to be tough to undertake. Gumi really need to sort that out and also all the server issues they're having, I've lost prizes and battles I've won because the game couldn't connect online!