I have had mine for over a month and no scratches, I ware it all the time even doing yard work. I wash my hands with it on, I wouldn't be worried about the occasional splash but I personally wouldn't submerge it, although it would probably be just fine. I think I read that some have gone swimming with it on.
Screen looks good after 2 months. It's Gorilla glass, so it does have limitations. I do my best to keep it away from things like sand, so I don't wear it to the places like the beach.
Waterproofing is fine for daily wear. Washing your hands is no problem.
I use a screen protector on mine, because you never know when your wrist might brush against something unexpected. Also, this watch is thicker than my last one so I figure it's kind of more in harm's way.
I had one which managed to get 2 parralel scratches on the screen. I couldn't feel them but could see them clearly when under any bright lights.
I returned that watch and replaced it with the same but put a glass protector on straight away. I got the Fiimi one from Amazon and it's really good, slim and easy to apply.
Glass on my S2 is fine, but I managed to swipe the bezel against something and I have a small nick, and a few minor scratches. I have to stare at bezel for a few seconds to see it. Dark grey sport version, and more than two months, and mine looks like new as long as looking at it from more than 3 inches away.