Once more, this thread is going to focus on the look...
As already said many times in many threads, maybe look is good to appeal new 
comers...
But whether windows should be green or orange, or the button have thick 
borders, oval corner or a shadow is not the more important.

What is more important is feel.

I do not know how good is Squeak UI on Mac, but windows and linux squeak feel 
are not at the level we would expect such a wonderfull tool. I will take 
several simple examples.

Why does the mouse wheel does not scroll lists but instead flash? Why does the 
pageUp and pageDown keys also flash the list instead of selecting one page up 
or down? Is there multiple selection list working with kind of shift+click or 
control+click?

How can i switch keyboard focus from one pane to another, or change window 
stack order without using the mouse?

Did you really try to copy/paste text from squeak to another application et 
vice et versa? switching from ALT+C to CTRL+V, or the contrary is really is 
gymnastic for user hands and brain... That is obviously why a little bit of 
standardization does not harm.

My personnal opinion is that among palo alto inventions, the mouse was not the 
greatest. Hands are wonderfull tools with a lot of articulations. Compare how 
many articulations are working when hitting the keyboard and how many when 
using the mouse... You will understand why many feel the mouse as a handicap. 
And why many are still using emacs vi and mc.

So, when you say "the look does not matter", or Squeak UI is great, please 
don't forget the feel. Lot of people won't find mouse-centric UI that great.

Nicolas