That was the brilliance of NEXT: leverage momentum of UNIX in lower layers while hiding it behind a sensible upper layer. Fixed up the graphics stack, attempted to provide better organization (failure = Mach), and provided consistent, good user interface on top. Maybe better API's, maybe not... never programmed Macs.

I've been saying for a while that a group needs to do this for one of the BSD's. Not just put KDE or Gnome on one but seriously reengineer the GUI, sounds, graphics, admin controls, and package mgmt. Smooth integration with high usability and good efficiency like Macs. Closest I've seen was Mint but had to ditch it for security reasons.