The concept is quite good, but the problem is that...well, that's it. Once you've mastered the tricks, the monotony of routine sets in. Your Sim barely requires any care, so once her quick needs are addressed, it's off to the spa, spending the day caring for animals with the same problems and treatments, over and over again. Then your Sim goes upstairs, maybe plays some minigames, and goes to bed. Rinse and repeat. Unlike in the PC Sims games, your Sim can't go anywhere, make friends, or do anything, you know, fun.
Sims' lives revolve around the pets, the spa, and decorating. Ultimately, that's not enough to fully disguise the dull task that caretaking becomes, and the cycle runs its course after only a few hours of gameplay. Kids may be drawn to the cute critters, but in that case, they should spend their money on a game that balances cuteness with fun more effectively.