Disappointing, glitchy - stick with the PC.
There was very little of the original gopets charm left in this game, most had been squeezed out to make way for HORSE pets and villages. GoPets has never had Horses available for pets; it's always been cats and dogs. Even the animations are nothing like what the should be on the older MMO version.
The game is incredibly glitchy. Problems rose with shops restocking, multiplayer play, levelling up... Pretty much everything that could go wrong, did. If your daylight saving time changed on your DS, the shops would stock restocking which was pretty dismal to try and 'level up'.
The online play was something a little better, something small I liked about Vacation Island. Connecting to wi-fi allowed you to make friends with other players, invite their pets, send your pets - exactly like the MMO version. It probably could have worked terrificaly too, if it wasn't so glitchy.
For someone who has never played the MMO GoPets, although your expectations may not be as high, you'll probably still be disappointed with the flaws, the glitches, the empty storyline and the untidy graphics. Oh, another thing too! Using your stylus to move decorations is crazy hard. I thought it might need calibrating, but turns out if I want to move my bathtub, I actually have to press a few mm down the screen to select it.
My conclusion? If you want to take care of some virtual pets, stick with the PC version or go back to Neopets.