People have learnt to manipulate the rating system so its no use. It looks pretty and that's about it in my opinion.
We've all seen it happen at places like Rendo when really good art gets nowhere because the artisit is not a member of a clique and people who have produced really not very good art have shown in the top ten because they wee voted on by all their friends.
A lot of people have the feeling that if someone votes for them they have to automatically go and vote for that person whether or not their art is good. That's why rating sysems and particularly anonymous rating systems don't work.