Finally. A new style of non-AvCom MMO that actually works. Sorry Dofus.
Beyond that, the main quest is challenging, rewarding, and will keep you busy for a long time. The crafting and market system is as good as any MMO I've played.
The Guild system is surprisingly well plotted out. With guild ownership of towns, including tax collection and special buildings. And of course plenty of reasons and opportunities for Guilds to go to war with each other.
Atlantica also offers, what seems like endless PvP tournaments, and a ranking system to match.
Again, nothing wildly new about much of that, but those are a lot of classic features that are handled with great competence here.
So if you're tired of the old AvCom MMO grind system featured in a 1000 other template games, you'll probably find this one very refreshing.