The only advantage to DS4 at the moment is that it behaves better with bigger scenes, in terms of moving around the interface, DS4 feels slighty faster loading and saving, but when rendering those scenes the speed is the same as DS3, the quality is the same as DS3 and I've gotten it to crash as well. So interface has loads of room for improvement, there is no reality render option, there is a new light option; Linear Point Light, and I just found this which looks pretty neat

http://www.youtube.com/watch?v=DW1JrQ0BNV0