Be nice. Or else.
I'd like the ability to remove an upvote I've given (in case it was accidental, or I realize it was a duplicate post or what have you), and also to see a list of all the posts I've upvoted (perhaps this could live in the profile that many people have requested already).
Maybe comment upvoting as well, so a thread with many comments will have the most relevant or insightful comments first.
Not a big concern while it's still growing, but a bit further down the line search would be nice (though it's hard to do well), and maybe filtering by type of posts (badges) or time.