Some features just on the top of my mind in no particular order:

* Edit relays

* DMs

* NIP-05 support on profiles

* Click on a reply and display the whole thread

* Search for users based on either pubkey or NIP-05 identifier

Less important but nice to have in the future:

* Edit LNURL in metadata

* Lightning payment button on the profile page if the user has set the LNURL field

* Render BOLT-11 invoices

* See which relays other users are connected to (Astral supports this today)

* See followers/follows for a user (Astral supports this today)

* Boosts show up just like a retweet on Twitter

* When I write the '@' symbol, give me help to find the user I want to tag. Astral does this pretty well today.

* Freetext search for users

* Connection status for relays. Makes it easier to spot dead relays.