Mobile

I installed several iOS nostr clients, Damus, Primal, plebstr and Iris. Basic functions are all working great, like feeds, comments, notifications, messages etc.
Zapping is the most notable problem, maybe because of Apple's restriction. Some only support zapping user, but not posts (Damus, plebstr). Some do not have builtin wallet support, you have to use a third-party wallet (Damus, plebstr, Iris).
So far Primal is the most convenient. It has a builtin wallet, and support zapping user and post.

Web

I usually use Web-based nostr client, like https://primal.net/ , https://coracle.social/ , https://iris.to/ . https://coracle.social/ is my favourate. I like it's design and the feel of it. And it seems to be most feature-complete. https://primal.net/ does not support zapping user yet.

Desktop

Never tried any.