My conclusion was (and still is) that Media Pro is not ready for release yet but it seems that you do not have any other choice than to go with MP1.
Apparently you can still download a trial version of Expression Media from Phase One's
Microsoft Expression Media archive page.
Not sure how much it costs to activate a full version, but I would definitely try Expression Media first before attempting to use Media Pro. But if you use a Nikon camera and Nikon software, prepare for disappointment as Snow Leopard doesn't support NEF edits made with Nikon software.