I just posted a review yesterday in another thread:

"I used it in SFO. The only thing that was an issue at all is that they have a location offsite. You still take the train to the rental car stop, but they pick you up from there and take you to the offsite location a few minutes away. When dropping off the car, they will take you back to the rental car stop. The Audi A4 was nice, included navigation and all the bells and whistles without any additional charges or that huge Hertz screen that gets in the way. The pick up and drop off are very streamlined and primarily use an app, but you can also call them. Price was also very competitive - was actually lower than full size from Hertz the time I rented.

The service was good enough that I booked a Silvercar again for next month and will be using them wherever they offer service.

I have a referral code if you need one as well."

Silvercar is excellent and is offered at SFO and LAX. I've been a Hertz gold member for a number of years as well but with Silvercar's pricing, I don't see myself using Hertz in the future unless Silvercar isn't available in the city I'm flying to.