I have seen a rating control in JavaScript/HTML Project for windows 8 . BUt I couldn't see anything like that in XAML yet . :(
Any idea how to achieve rating control in windows 8 ?..
Seems like Microsoft treating XAML guys as second guys :(...
I ported an open source control for displaying ratings with stars from WPF.
Maybe you can start from there, or find it useful.
http://igrali.wordpress.com/2012/05/20/show-ratings-with-stars-in-winrt-xaml/