First of all, I have played all Atelier series released so far, whether English or Japanese.
Comparing to all other Atelier series, Meruru has the best system you can ever hope for.
Its graphics are high as well, but as most Atelier players would know, Atelier series isn't all about graphics.
The system is very important in the game, and Meruru uses the simplest and yet the most entertaining system.
Your friendship with others are easy to build, you can check your Quests right off the main menu, synthesis menu is very well organized, battles are fast paced.
The goal of the game is to successfully enhance the country before the end of the 3rd year, and other than that you are not forced to do anything.
Various characters lets you experience unique events, and multi-ending system will make you to complete all of them.
For your 2nd playthrough (New Game+), you can skip through the events quickly with the CIRCLE button, allowing you to skip any events you have previously seen, or replay them.
As the Atelier series fan, I love Meruru, and will rate it as the top of the list.