The proposed optimizations are pretty interesting, but I think my favorite such optimization has been proposed by Ayende Rahien. As with the optimizations outlined in this paper, his is related to leader election.

One of the issues with leader election in Raft is the potential for split votes. Raft tries I guard against this by randomizing election timeouts in order to discourage two candidates from requesting votes at the same time. What Ayende suggests, though, is to add a pre-vote stage wherein followers poll other nodes to determine whether they can even win an election prior to actually transitioning to candidates and starting a new election. This ensures that only up-to-date followers ever become candidates and thus prevents nodes that will never win an election from ever transitioning to candidates in the first place.