1. Not getting clear messages as to why when relays reject or filter a note.
2. Not having a single sign on solution (secure private key management that works across all clients)
3. Not easily seeing the reach and distribution of notes and user info / no good network wide search. I spent a lot of time trying to find and connect to some friends  by their NPUBs at first without knowing which relays to use.

Why not implement a relay level DHT index of note/user hashes <-> owning relay that could deliver a federated search across participating relays?  (https://libp2p.io/implementations/)