I think it's worth correcting your use of "Uncanny valley". My understanding (see links below) is that "Uncanny Valley" refers to virtual beings trying to trick you into thinking they're real but coming off as creepy instead -- e.g. the Tom Hanks voiced train conductor in "The Polar Express". Creepy. See here: http://en.wikipedia.org/wiki/Uncanny_valley and the new yorker article here: http://www.newyorker.com/magazine/2014/04/28/pixel-perfect-2

It does not refer, as you suggest, to the general case of VR not seeming real. There is a special thing that happens when we see fake beings trying to pawn themselves off as real. It think it's worth preserving the distinction.