I imagine such a brain upload process would be rather traumatic. Assuming it works reliably, what sort of physiological trauma would you now have? So many people associate themselves with their body, how they look, what physical things they do (sports, gym, etc)... and then suddenly they are just their thoughts and whatever external stimuli we can simulate. I guess we could simulate those things in VR, but even so, deep down you will know it's not "you".