Unless PS has been updated to make this a feature, i may have found a bug. Now (in CS6 vs. previous versions) when you duplicate a shape layer, if you had previously selected specific points of the shape (for example with the direct selection tool) only those points will be duplicated in the new layer. This is true no matter what tool you are currently using.
What I did was make a rounded-corner rectangle shape -> then direct selected all points on one side to stretch the rectangle without distorting the rounded corners -> then switched to the move tool so no points were selected anymore and only the layer was selected-> duplicate layer (with the intention of duplicating the whole shape). what i got was just the rounded corners on a new layer.
It seems the only way to duplicate the shape layer in its entirety is to go back with the direct select tool -> select ALL points of the whole shape -> change to move tool -> dupe layer.
If that's the intended new functionality, it's a bummer because if you intend to only duplicate certain points, you can already do that while using the direct select tool. Using the move tool, it shows no direct selections and therefore you should be able to duplicate the whole layer.
Maybe I have some weird default option checked that I'm not familiar with? This is not how any previous versions of PS worked and will add friction to my workflow if this is new.