Les Yay: As usual. If you think Totori and Mimi going Les Yay on each other is enough in the previous game, try putting Meruru between them.
Surprisingly Improved Sequel: Generally the reaction the game got on both sides of the Pacific. In Japan it was the highest-reviewed Atelier game since the original release of Atelier Marie all the way back in 1997 (until Escha & Logy took that crown, anyway), and it's the best-selling Atelier game in ten dog's ages. The reaction was a little more varied among critics on the other side of the pond, but the high scores remain among the highest the entire franchise has ever seen in Anglophone publications by a county mile.
The Scrappy: Rorona. She got turned into an eight year old between games, acts her new age, and her memories have become a complete mess. Though her Alchemic skills are still intact, she mainly refuses to use it willingly. A very large portion of fanbase was not happy with this turn. This is apparently because Gust couldn't stand to see her in her 30s. "Who wants to see a Rorona in her 30s? Not me, that's for sure!"
Astrid herself receives almost as much heat for doing the deed. Two of the endings make it worse! In one ending where you make a Youth Potion that restores her normal age, Astrid sabotages it to to only age her back to 14 with her memories still a wreck, with Astrid delivering the above message. In another, Witch's Tea Party, she forcefully renders all 3 Arland protagonists and herself to be 14 forever, citing it as an "ideal age". Some fans even treat the endings as the Moral Event Horizon.