A big thing is I'd like to be able to follow the public timelines from other instances, so I can have a more controlled firehose than just the federated timeline.
I usually read my home and local timelines in bulk in the morning while waking up and after work to get caught up on the day. None of the clients I use handle reading through 8 to 14 hours of posts from hundreds of people all that well for some reason. I'd also love to have a "randomize" button lol.