His objections appear to be:
He doesn't like Ubuntu switching away from GNOME (presumably 2) by default. Except that Debian have moved to GNOME 3 as well, which is why GNOME 2 is no longer available in Ubuntu. However, GNOME 3 is available in Ubuntu, so all he's really complaining about is the default.
He doesn't like Ubuntu One, except that in Ubuntu it's merely something that's available. Your experience is exactly the same as Debian's if you don't use it.
He doesn't like Ubuntu Software Centre. Except that you don't have to use it. apt-get and Synaptic are available and work just fine in Ubuntu. Software available from the Software Centre includes software not part of Ubuntu itself. Thus it doesn't violate any rules about Ubuntu itself. Debian is the same - third parties publish .deb files, and these don't have to comply with any Debian guidelines either. Yet Debian ships dpkg, which allows one to install them.
He complains that he can't find the "Ubuntu Manifesto". I'm not sure of the exact document he's referring to, but the principles he's referring to and quotes can be found in one click from http://www.ubuntu.com: http://www.ubuntu.com/project/about-ubuntu/our-philosophy [edit: apologies, two clicks; "About Ubuntu" and then "Philosophy". Still, not exactly hidden]
Then he complains about Unity again, except that he doesn't need to use it. GNOME 3 is available in Ubuntu, along with Xfce and LXDE, and you can get these by default if you use Xubuntu or Lubuntu install images.
Then he complains about Ubuntu not focusing on privacy. Ubuntu introduced a single central place to manage your privacy settings in 12.04 (http://www.omgubuntu.co.uk/2012/02/privacy-controls-minor-ui...). The privacy settings he's complaining about can be controlled from here. Again, all his complaint boils down to is what the default is.
So, given that everything in Debian is available in Ubuntu, his article "Why I'm Leaving Ubuntu for Debian" can be summarised to one word: "principle". And perhaps you might want to add "defaults", except that Xubuntu and Lubuntu are available and provide defaults that eliminate all of his complaints.
He's entitled to this view, of course, but the rest is FUD.