I went to the site, and it didn't work! In any case, that's just a few guys "expert" opinion.
We should learn from the titans. Learn from their success factors and their mistakes. Research the web for articles on usability testing regarding OS's.
Then make som mock ups and test their functionality. Have other users test it - and not just the Amiga community. Hardcore amiga fans will hate a new contemporary look - they will feel as a part of Amiga dies. Let it be so - we can't live in the past, we have to move on. And that is, as I have mentioned before, to be creative, think new, think different.
How can a GUI be designed to make it usable?
Can the OS support different levels of knowledge? (e.g. a built in function that sets the "difficulty" on menu options according to if you are a novice user or an advanced user)
Does the GUI support 1,2 or 3 mouse button actions? How does the windows layer themselves?
And the list goes on!
Hm... maybe we should start a thread that lists and discusses areas that will improve a future GUI?