I would say the main ones were difficulty finding apps and keeping them up to date (I ended up with three different ways of doing this, and it was hard to remember which was used for each app), certain apps that I needed to use not working (banking apps), unreliable push notifications for things like Signal, lack of good degoogled navigation, and battery drain. There were also a lot of little things like how much easier is it to work with the camera / photos on iOS.

Overall it was workable and I liked GrapheneOS, but just decided the trade offs weren’t worth it.