I've dropped my Mozart a couple times and I have 3 deep scratches on my screen. I didn't think it was gorilla glass as I thought it was tougher. Although some of those drops were from quite a height and the screen is still in one piece. The Mozart is one tough cookie but I would recommend using a screen protector and possibly a case just to keep it looking beautiful.
Current phone: Nokia Lumia 1020
R.I.P.: HTC Mozart, HTC HD2, HTC G1, Palm Pre