Only 2 problems I have with Graphene personally is the need to give Google money, which the irony is just too much, and no option for rooting. Otherwise it seems like a pretty good OS overall. In the meantime, while I wait for those options to be more flexible so I can have full control, I just use a rooted lineage os with all the extra Google stuff (ntp, DNS, etc) stripped and replaced with my own self hosted systems.