Photoshop’s submenus, window management, and setting 
  screens afford that software package a level of feature 
  depth I don’t believe can be achieved in a mobile 
  environment no matter how sophisticated and intuitive UI 
  conventions become.

I wonder if the author is aware of Photoshop for Android tablets - https://market.android.com/details?id=air.com.adobe.pstouch

Granted, it doesn't have all the features of desktop Photoshop, but it looks like it has a lot of the features, and it has great ratings.