it will be interesting to find out how Apple plans on tackling the little problem that those who install via physical disk and not the MAS, cannot update the software after upgrading to ML. As far as I can tell from using the DPs of ML, all updates are going through the MAS and not the traditional Apple Software Update.
This is a problem because whether I run Lion or and of the DPs of ML, if I install iWork from my disk, the MAS versions refuse to acknowledge that it's installed.