Ralph Furmaniak created a site based or reditt where people can leave comments and up-vote the arXiv papers. See discussions at
http://publishing.mathforge.org/discussion/83/frontend-to-the-arxiv-httparxalivorg-based-on-reddit/
http://arxaliv.org/r/help/comments/12hd/welcome_to_arxaliv/is
I think this is great, unfortunately not so many contributors, let us contribute ?