I'm a huge Atelier fan, but I didn't like it as much as most people seemed to.
The story was very forgettable (even by Atelier standards), Lulua's motivation to do that much for Stia is not believable etc.
It's also much too long, as it usually is with the later games.
The bosses aren't satisfying to beat for me because it's either they feel artificially difficult, or so easy that you just spam your best items until it dies. I typically play on easy because I don't care about "challenge" in Atelier games. It never feels good.
Interactions are great though, as usual, and this game has some of the best comedy in Atelier. Plus, all the returning characters from Arland made me happy, even though the whole game felt "extra". Seeing Rorona, Totori, Meruru, Sterk, and especially Pamela(!!!) was great.

Below average Atelier overall I think.