I own all three consoles, and I find NXE to be much worse than XMB or Wii Channels. The Wii Channel interface is a good example of a good simple interface designed for children and inexperienced users. All the complex functionality is available, but designed in a way that it would be difficult for a Child to easily manipulate it. The user accessible stuff however is easy to find and with large icons. I would consider the Wii layout to be on a similar mission as Mac OSX and generally successful in exposing the limited functionality provided by the console.
I also like XMB, because it is logically arranged in columns, has a generally pleasing and consistently designed layout. I would consider to be a good power user interface, similar to a Gnome setup on a Linux System.
I have always found NXE to be needlessly garish and cluttered. At first glance it looks easier to use than XMB due to the large icons and such, but the way is arranged is totally illogical. Need to change the theme, no it's not under My Xbox, as you expect. You have to Click on your Profile and change it there. Need to create a new Gamer Profile, sure do it under My Xbox as expected. Need to delete one you don't want, sorry, you have to go to storage settings. Need to pair a controller, sorry, can’t do it in a menu, need to press the little button on the console instead. Why, why, why?