This is spoiler free, don't worry.
I'm about 5 and a half hours in, I've got 2 Venus, Mercury, and Jupiter Djinn, and 3 Mars Djinn, and also found 2 Summon Tablets. I have to say.. much like the 2 before it, which pushed the graphical limitations of the GBA, Dark Dawn does the same for the DS. The graphics and animation are amazing, with all characters and enemies being fully animated 3-D models each with their own item using, spell casting, attacking, and death animations, and it all goes together beautifully. Everything feels very fluid, and the spell animations are some of the best I've seen. Not just on the DS, but in RPG's in general, and the summons... oh man, the summons. They are absolutely amazing looking.
In terms of gameplay, it's everything you've come to love from the previous Golden Sun titles, and so much more. New puzzles, new Psynergy granting items, expertly designed dungeons, and cleverly (almost mean) hidden Djinn. The combat, of course, is the traditional turn based battle system that the Golden Sun series has mastered.
Now, for the people who have not yet played this game.. think for a minute how good this game will be..... go ahead, give it a nice thought.
Now multiply that thought by 10, and you've got about half the amount of SuperAmazingAwesomeness that Dark Dawn delivers.
If you have played (and beaten) the previous 2 Golden Sun games, this game shouldn't give you too much trouble in Japanese, if you do not know the language. The downside, of course, is not being able to understand what people are saying, which is a very pleasurable part of Golden Sun. You'll still be able to tell what's going on in terms of story, though.
My score for the game is... (Let's see.. my thought of the game is "It will be amazing".. so now I gotta multiply that by 10... which gives me... Super DUPER amazing... okay, let's go with that)
A "Super DUPER amazing" out of 10. And remember... that's only half of the amount of awesome this game delivers. Oh, and there are 83 total Djinn to collect. Let that sink in. Eighty-three.