sbruno,

I answered your question about the lack of processor query APIs over at http://social.msdn.microsoft.com/Forums/en-US/tailoringappsfordevices/thread/8e035ad1-10fc-465b-b930-d38edc875272

I will just link to that here to save typing it all out again.  Hopefully this clarifies how you should implement multicore optimisations in Metro.