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PackageKit is available in Intrepid's Universe repository.
I see that as a disappointment, because I thought it was going to be pre-installed and help make better updating, as one of Intrepid's blueprints said. Just providing it in Universe will not do anything, I assume, because users won't know what to do with PackageKit or what it is. (In fact, the specs say work hasn't even started on it. #$?@*!.....)
I hope Ubuntu will pre-install it, and then maybe I can rejoice and update this post to include more details.
UPDATE: Work has started! Please help test in Hardy and Intrepid by seeing here.