This is a pretty good overview of some key deficiencies. I wish he would have left the "not backwards compatible" complaints out -- backwards compatibility is a well-known non-goal, and it's a non-issue how difficult (or subtle) porting code to Py3 from Py2 is.
The super() stuff is unfortunate. It seems that Py3 manages to clean up so very many other uglinesses of the language... to see a new, obviously ugly thing introduced...