Unless the 1080p monitor is a CRT, yeah it'd look pretty blurry.....more pronounce when going from a higher resolution monitor down to 720p....like 1600p to 720p.....eww....hahaha But of course if it's played in window mode, aspect ratio will be intact, rather than stretched to fit your monitor size and scaling would be 1x, not 5x or how ever many times it is needed to make it look fullscreen on your monitor....