I use Private Relay on and off and find that it has its plusses and minuses.
Pluses:
- as a VPN substitute, it allows me to open some sites that are otherwise inaccessible to me in a normal browsing mode;
- it gives an enhanced browsing privacy, as neither Apple nor the end-site know who is browsing and what.
Minuses:
- some sites slow down considerably with PR enabled;
- some web-based platforms/services simply do not work, a good example is snapdrop.net
So nowadays I only use PR if I cannot access a website for any reason and it usually helps.