The main reason for me to have a 1-10 scale is to get a clearer picture on the upper end of ratings. Many pieces are given 5s where as 4s are reserved for "almost great." With a 1-10 you now have the option of starting with 6 as "almost great" going all the way up to 10 which would be "the best of the best." The biggest question of gallery ratings is how much critique do you really want to see? Since there is a wide diversity of both amateur and professional artists here critiques can be taken the wrong way if a person isn't used to it. I've seen some members requesting more critique info so they can improve their work. Having a 1 to 10 rating system will help with that.