Depends on what you want. PCars is a fantastic RACING experience for the Xbox One -- better than Forza 5 -- when it works right, which isn't very often. But SMS, even with its snark, has issued four patches since release in mid-May, with another in the works. The fact a game needs five patches within two months of its release is telling, but at least SMS continues to chip away.
That said, if you want more of a Forza-like car-collecting and driving game, steer clear of PCars. Give it a few months for the bugs to be killed, and you'll likely see a lower retail price, too. It won't be long before PCars is $39.99 or less at retail or on Xbox Live Gold.