I agree with what every one said here, the rep gives the author a general idea of what a group of people think of his/her post. but I think the XP is wasted. To me XP implies that you've learned something, and if the XP is based of the rep of your nodes and you using all your votes, then the XP gained in no way says any thing about you except how active you are at this site.
With the downvoting, I think it would be nice if a person would be asked to give a short comment on why they downvoted it, and have that comment sent to the author. I know I would like to know whats wrong with one of my post, and I think most people here probably would too, since most people wouldn't write a bad post on purpose.
learning Perl one statement at a time.