Ensemble Darkhorse: Solle, as a new, non-returning character from Ayesha, was placed the highest after Logy and Escha in the official popularity poll.
Even Better Sequel: At least according to the review circuit. In Japan, it's the highest-reviewed Atelier game ever made. Period. It was similarly the entry with the highest aggregate rating on Metacritic, and still has the second highest by a difference of one pointnote technically it ties with Totori Plus, but T+ barely even breaks the necessary 4 reviews to place, while E&L has twenty-six reviews, the highest number since Iris 3; even the "new queen", Rorona Plus, has fewer, and brought in the first perfect score the franchise has ever seen on that aggregator. And as ever, while the actual average may seem a little on the low end, it's due to the ever-present problem of some critics just not understanding the game - the high scores stand among the very highest the franchise has ever, ever seen outside of Japan.
Funnily enough, though, among fans this status is a little more debated - some fans take issue with a few elements (like Logy's central position to the plot), as outlined on the main page and think somewhat better of Meruru or Ayesha.
Game Breaker: Having the homunculi clone a Purple Crystal with multiple traits that increase its selling point at shops makes it very easy to rack up massive amounts of the game's currency, Cole. Not only that, but you can use this money to buy benefits that directly increase your stats and alchemy abilities, as well as other benefits. Additionally, any money you have at the end of the game will carry to a New Game Plus, meaning that you can start getting great benefits right away. For that matter, New Game Plus is pretty much just easy street if you some time crafting the best equipment, or even semi-decent stuff. You keep everything you have equipped to your character in terms of weapons, armor and accessories and can buy back synthesized items you had equipped about halfway through. This allows you pretty much just rout any enemies you come across for most of the game.