I can only comment on mossy Escondido. A few years ago they replaced the intake manifold on my 09 wagon and believe it or not, also my entire DSG somehow using the TDI warranty. Drove the car over 20k since those, no problems with these repairs.
Also just happened to drop off my 15 Passat for a whining fuel pump which will be warranty work again. The previous service guy isn't there anymore and I found out they're under new management (they used to give me a rental by Hertz, not anymore). I don't expect any issues from a fuel pump replacement.
A few months ago, I took in my Passat to Puente Hills VW for a emissions related warranty repair. Lets just say it wasn't a pleasant experience and in the end they couldn't fix the problem. I took it closer to home to San Bernardino VW and they fixed it fairly quickly. The front desk staff were super helpful and knowledgeable. They even made me aware of my rights per the settlement agreement.
Darn it, I forgot to update y'all on how my service went. Well I dropped in for my appointment on a Thursday at 9 am and they got me processed in right away, Michael was my advisor. So that was done and he said no problem you are covered under the warranty also they did one of the service bulletins and replaced the chrome on the gear shift, anyway, a few hours later he let me know that they didn't have the DEF lineset and would have to order it, he gave me two options, come back or we will get you a rental car. Well since it's a long drive from home to the dealership, I chose the latter. So they called Enterprise Rental to come pick me up and shuttle me to the rental yard and they said pick whatever car you want VW is paying for it, so I grabbed the Chevy Traverse and it was a loaded one. Four days later my car was ready and no more leaks from the DEF injector. All in all, I'd say it was a good experience and I would recommend them.