I've got about 15 hours into this now. I like it more than I thought I would!
The leads are super irritating, no question. God I hate their designs, chibi and regular.
I don't like the chibi designs in general, really.
The "world map" is super disappointing after the trailers that made it look more DQ8-ish.
The writing is often groan-worthy. The plot is incoherent, and the way all the classic FF characters are shoehorned in is bizarre.
All that said, the monster collection and evolution is pretty great, and the dungeon environments are really pretty and generally fun to work through, catching monsters, finding secret areas, taking on optional mini-bosses. The music is good too (no surprise there). And, even though the way it drags down the already sloppy plot is a shame, the FF character fan service is solid. The old heroes don't just show up but actually show personality, and it's a treat to see old favorites pop up.
I'm mostly left wanting SE to make a new FF (not a fan-service fest) in this style (but with a much expanded world map).