I haven't had any experience in the USA, but I would say that in France (my homebase and where I mostly rent) and in Germany (where I also often rent), the benefits are obvious.

I've been a regular Gold for years and got one class upgrades about half the time. Since I reached PC, it has always been "Which car would you like ?", "We have upgraded you to xxxx, but would you prefer something else ?" and at CDG airport, they don't even check my licence anymore. And I regularly receive PC Free Day coupons, which can be valuable.

This week end I booked B (Opel Corsa) and received G5 (Peugeot RCZ). Applied a Free Day coupon, so paid 22€ all inclusive for two days in a nice roadster. PC is good to me