Not bad, not great either...
To spoil the fun on the beginning ;) - while Golden Sun is not out yet, I hope FF 4heroes is the worst of the trio, because while game isn't bad... it's still disappointing as hell!
Story and quests are ordinary - almost boring. I know this kind of messing with all time classics should be funny, but it's not executed well enough. DQ IX delivered it soooooooo much better. Most of the time I couldn't sink in to the game, making mindless quest and grinding over and over again. It have a nice touch, some good ideas, but not enough. Not even nearly.
Gameplay and battles - nah and... naaaah. In matter of fact - that's the weakest point of the game. Battles ain't bad, but the system is weak. Not so intuitive, not so enjoyable... and worst - not flexible enough. Well - I'm comparing with DQ IX and older DS FF games at this point.
Graphic and art style. It depends what You like. Art style is really original, and I loooove it! It works for me and in my opinion it is the strongest point of this game. What is sad - I don't care for graphic much, but it's nice to see that someone is still creative here. But let's be honest - DS is not a platform You expect to have groundbreaking graphics, so if something like this happens, I have to rise score!
Overall - if You don't like the graphic style, this game don't have much to offer. You can buy egzacly same gamplay for much less in other titles (mostly FF). If You (like me) love this kind of adorable art style - it's worth to consider, 'cose game is good. Not best, but still it's good.
At the end! If You're short on cash, and willing to buy only ONE rpg for DS... make Yourself a favor and spend Your money on Dragon Quest IX. It's better on every point You can think off. Maybe not the graphic style - but as I wrote before - depends on what You like. But think of what we love, and what we love is gameplay - Good. But DQ IX is some 10 times better.
Now waiting for Golden Sun ^^