we aren't sure yet whether pixels will be sharp or soft when fullscreen. I have always prefered softened when i play pixel-art games such as emulators, i find the sharpness to be much more "headache-inducing." Im going to ask fil though if we can make that a visual option that can be on or off.
For comparisson, just double click the small image here for a rough approximation of fullscreen sharpened, though as you can see, it isn't going to fit perfectly with nearest-neighbor, about 14% of the image goes off the sides of the screen with that or there is a massive gutter (if you are any of the standrad resolutions)