What I'd love however are these two features:
1) The ability to be notified that a user you are interested in "following" has recently commented or posted.
2) The ability to see which comments/posts of yours have been upvoted or downvoted in chronological order. (Sometimes I will sit with a static karma number for months and then I'll see a surprising +1 but fail to decipher which of my historical posts suddenly got upvoted. It's a good feeling but I'd want to know which post was responsible.)