There is nothing wrong with this game but there is also very little new to this game. I've followed (and almost universally loved) the series since its debut on the Super Nintendo. This game is a retread of the last and the levels of complication they add do nothing to enhance the game.
If you haven't played Harvest Moon before, or just didn't play the previous title on the DS, I absolutely recommend the game. If, however, you bought the last one - just play it again.
All three of my children, ages 7 (girl), 9 and 10 (boys) really enjoyed this game. All three of them have DSi's and they couldn't put it down. Normally my boys are Halo, COD, Assassin's Creed gamers, but they actually found this fun. I'd say if a game can grab the attention of more serious gamers, then this has to be worth trying.
I gave it a 9 because these days everything has an option of multi-player and it is only single player at the moment. It would have been even more fun for my kids if they could game together.
All in all, the kids loved it (its about what they enjoy, not me) and I enjoyed the quiet travel time in the car! What parent wouldn't rate that a top!?? =)