It's not playable without patch. When it comes to the technical stability, the Pet is the worst expansion pack ever...
After 6~7 hours, the game starts to bring hidden glitches. It starts normally the lag or the dragging of the motion and finally becomes freezing. Once freezing appears, no one can stop or change the situation even though you start the game again.
In addition, some users have graphical issues such as invisible fur and distorted shapes of pets.
To my think the pet expansion pack isn't optimized and finalized for the end users. It's like the just beta game product.
Everybody is waiting for the patch. But for two months (since the launch of the Pets) EA did not show any efforts to fix the game.