My experience is the apps are missing very fundamental features. Which would be fine... If you could use other clients. But you can't, except for email, kind of.

Like, the calendar on mobile doesnt even have a search function. What if I want to know when an event is happening? I just have to scroll and scroll until I find it? Come on now. Also no storage backup in proton drive??? What??? That's, like, 90% of the purpose of proton drive!