Well, I think it makes sense to not be able to see the XP before you vote. In theory anyway this should help you to be more objective and give the node the rating you feel it deserves instead of just "following the crowd". However, sorting the nodes by Best does kinda defeat that.

Perhaps an option to show the XP for a thread if you've used up all your votes for the day (or can't vote) or if you don't want to vote on that particular thread would work?