I've upvoted by mistake, and have never noticed any later bad effects. I've downvoted when I meant to upvote before, however, and it's been frustrating not to

I've upvoted by mistake, and have never noticed any later bad effects. I've downvoted when I meant to upvote before, however, and it's been frustrating not to have a way to counter that. That said, I tend to upvote about 10x more than I downvote, so it likely balances out.