The nose gap is small but enough to look through. You don't notice it unless you look down at it. Hope this pic works to show it.
The limitations I've found with Rift CV1 is I'm short sighted so needed Widmo lenses as my glasses would not fit in. Vision is not as clear over distant compared to a monitor, also you notice the screen door effect caused by the lens type. When it's cold it will fog up and when it's hot you have a warm device on your face so you sweat. Also if you suffer from motion sickness or are afraid of flying, it will trigger those fears as if they are real. I bailed out of a MiG 29 at 10 kilometres once, I am afraid of heights and it scared me but just for a little while.
But you have natural head movement and everywhere you look you see plane. Your brain goes into over drive thinking "Oh my oh my god oh my god! I'm in a Mustang!!!!!!!!". I race sim and flight sim and it's coolest piece of kit I've ever owned. :)