After a week of using Mastodon, I think the feature I'd like to see the most is some way to restrict the service from showing me the same boosted post repeatedly.
For example, let's say I boost a post. I will see it in my timeline. A person I am following boosts it too. I see it again. Another person I am following boosts it as well. I see it again. And so on.
Ideally, once I boost it, it shouldn't come up in my home timeline again.