I've been using gOS exclusively for a couple of years and it's been great. I'm not even using the provided sandboxed Google Play compatibility layer, only open source software.

It took me some time to find alternatives to the software I was using before, but in many cases I discovered better options in open source.

The support is excellent, and the fact that I have the last word on my phone's apps is great. Current pixels come extremely bloated in the stock OS. You can't uninstall many of the apps, and Google Play store has "super admin" privileges, so it can do whatever it wants on your phone.

The only negative I can see using GrapheneOS is that when you reboot the phone it shows an ugly screen saying you are booting a different OS. That's it.