After playing and sinking a lot of hours into this game already, I must say this is one of the greatest portable experiences I have ever had, especially on the DS, which is very weird. But here is what I thought about it.
PROS
-Level 5 did tremendous work on making such wonderful and detailed looking characters. Not only do they make Akira Toriyama's artwork shine in the PS2, but also to the DS in a nice portable looking fashion.
-Battle system is true to it's roots. Yes as always, the series continues with what they do best, staying by their roots. Yet this time, instead of random encounters you have to run into the enemy on the field. Yet there are always a lot of monsters on the field and dungeon, and a lot of them chase you and are usually faster than you. So your battle count will be just as large as if you were going by random encounters.
-Storyline. Yes this is definitely a very strong point for this game. Like other DQ's, the story has one main goal and you go through a series of helping people in need going from one town to the other. The story captures you from the beginning and the events you face through the game really does warm your heart.
-Multiplayer is fun and worth it on side-quests. Multiplayer is really not necessary in this game, since you can recruit people like Dragon Quest 3 and build your own squad. Yet if you decide to do multiplayer, you will not be disappointed. You cannot progress in the main story if you are in someone else's game, but you can keep all the experience you earned and any treasure you fine, so it is still a worthwhile experience.
-Character classes. Like Dragon Quest 7, couple hours into the game, you can change the class of your hero into Warrior, Priest, Mage, Minstrel, Thief, or Martial Artist. All of these classes are very powerful and useful in their own way, creating a great balance especially in multiplayer.
-Character customization. Not the most detailed, but has a lot of options to work with for a DS game, it will be hard for you to find someone who has the same looking character as you, assuming you decided to be creative.
-The humor. Yes, this game has a lot of it, and a lot of references to previous Dragon Quest titles. I found myself giggling to a lot of scenes.
CONS
-Silly hats. Yes, until end game, you will come across a lot of silly hats that are good to wear for the stats. I wish the developers made an option to not display helmets. It is hard to show off the customization I put on my character when it is covered by a helmet that looks like a tree stump. - -;
-Unimportant characters not 3D rendered. This kind of bugged me, and I can understand since you can only do but so much with the DS's processor power, but if you notice, and it is hard not to, characters that are not part of the main storyline are simply 2D sprites, instead of a 3D model. It really doesn't bother you, but I thought it makes my character feel a bit out of place.
-No voice acting. Again, because it is on the DS. I would of loved it though if this game provided voice acting. The voice acting that was done on Dragon Quest 8 felt flawless to me and entertaining and I can imagine how some characters on DQ9 would of sounded.
-No tension system. Dragon Quest usually isn't the type to bring something like this over to a new title, but it bugged me that enemies can still do this in the game and I cannot.
Overall, this is one of the greatest handheld experiences I have had since Zelda: Link's Awakening and would 100% recommend this to anyone who is a fan or even slightly played Dragon Quest in the past, you will not be disappointed in this title.