I just upgraded from Mountain Lion to Mavericks in Vmware 9 and all things works except restart.The system woks better in VM than ML.What I see new: No watermarks in the low right corner...
My impression is that although there are some improvements for the end user it is good to see that a lot of focus has been spend on the fundamentals such as OpenGL 4.1, improving memory use and finishing off the replacement of some of the old Frameworks with something more modern - AV Foundation and AV Kit being two examples that come to mind. I think the benefits will start to appear later on when Final Cut Pro X, Compressor, iLife and iWork are updated to take advantage of the new underlying technology - especially when one considers the new Mac Pro just around the corner.