This is a review of the anime only. I have not read the manga.
If ever an anime was a "kid's show," it's this one. That's not necessarily a bad thing, but it is sterile. It's a great show for kids. It's not bad for adult either, just, as I said, extremely sterile. And a bit saccharine.
What I liked:
1. It was an engaging and sweet story.
2. It was just romantic enough without being a Romance.
3. I liked that they didn't spend a lot of time on the ship but on the islands.
4. It had all the traditional Fantasy elements in a sort of new setting.
5. It was episodic, with each episode wrapping up and leading into the next one without a cliffhanger.
6. It had a touch of darkness in each episode but it rarely darkened the characters, which could be a good thing or bad thing, depending on your tastes.
What I didn't like:
1. It was sterile. I can't really go into more detail without giving spoilers.
2. There was one too-convenient plot devise that really didn't make sense. Again, can't go into detail without giving a spoiler.
STORY: The story's not unique in the slightest. It's an adventure story. One character is running toward something, two are running from something, one's wandering for the sake of wandering, and one's along for the ride. Pretty typical adventure group. That's not a bad thing, especially for a Fantasy story. It's predictable after a point, but that's not bad either.
ART: The art was pretty good. The panorama of the GrandCypher was gorgeous though the interior was pretty bland. The characters were distinct from one another with a good amount of detail. Many of the cityscapes were stunning.
SOUND: There were a couple times the music was too Fantasy or rather, too Children's Fantasy for my taste but it wasn't terrible. I did like the opening and ending themes. The sound effects were good.
CHARACTERS: These aren't real deep characters. They're archetypes more than characters but they fill their roles well and for the most part, are likable.
OVERALL: I enjoyed it. I'd recommend it if you can stomach the saccharine sterility. Definitely one of the few I've watched that I'd actually recommend for kids.