I continue to see bugs in the objects by performance and performance widgets in SCOM 2012 RTM through SCOM 2012 SP1 UR 2.
After selecting a group or instance of a class to target for the performance collection rules you want to show in the widget, the counters don't appear in the drop down box. Usually its the default "All" option that is returned. These widgets need some serious attention from the product group!