This is one of those shows that has been discredited by many viewers as a simple spin-off. Think it not a spin-off, but an extension. Before simply saying, "I have to make a choice between Private Practice and Grey's Anatomy. I can't watch both." Give Private Practice a chance.
The all-star cast is incredible. And Kate Walsh is even better now that she is in her element with actors and characters who are her age, and act like it. Grey's Anatomy's story now seems immature, and repulsively similar to high school in comparison to Private Practice's adults in their late thirties/early forties who are fed up with the crap of relationships. These characters have been divorced, been broken up with, and are looking for something of substance and meaning to add to their lives.
Yes, the individual episode format of medical conflict is similar to that of Grey's Anatomy. But more than just surgery plays its part in this show; therapy, alternative medicine, pediatrics and simple family medicine can be just as complex as surgery; often more-so since the patient is conscious and often fuels the issue with their personality problems.
So give this show a chance. The cast is great and the storyline is much more mature than Grey's Anatomy. If you don't try it, you won't know if you like it.
