I’ve never turned it off. Sometimes a website, like Grubhub for example, will think I am several hundred miles away from where I actually am. But that’s easy to fix. Otherwise, I’ve never had a problem with it.
I turned it on recently on all my devices and I’ve not even noticed a slowdown. Much better than when it was launched, and no need for a VPN subscription for privacy (I canceled mine and saved $100 a year ).
I’ve turned it off immediately because it does not offer any advantages for me. I use a pi-hole / DNS combo at home and use wireguard to always be connected to my home network wherever I am (nice feature of the wireguard client apps: enable when not on a specific network).
Because I run mac address based routing for my kid’s devices on the pi-hole (filter “bad stuff” etc) the features like mac address masking cause me more headaches than they solve.
The only times I’ve had issues with my network is usually when Apple’s devices turn on the private relay automatically and I can’t get on the internet at all.
I turned it on from the beginning and have never turned it off. Not even sure what it really does. I use Firefox or Chrome if a website has a problem with Safari, which bypasses private relay. But I’ve got no problems with any of the sites I frequent regularly.