OK ... I work in the software industry, particularly working with all kinds of different systems, and focused on a lot of UI stuff. the bottom line with a UI is that it is supposed to make things fairly obvious to the end user ... i.e. when I am trying to accomplish something ... PARTICULARLY something that I find relatively easy to do up to that point in time ... it should be fairly easy (and obvious) in the UI presented.
I switched back and forth between Apple iOS and Windows (specifically Win7) easily.
So the new interface was ridiculous ... and it took me much longer than it should have to "find my way back" to where I was comfortable ... the "desktop". I also find myself flailing around at trying to make my way back there when the goofy interface gets into certain "areas" ... particularly "full screen", working with images or videos or whatever. It is highly annoying. I also was not terribly please with my first foray into administrative stuff like user account settings and such.