Haven't seen any scratches on the GS4 yet, and I go to the beach quite a lot. My three-year old Droid X has two tiny little scratches on it, but maybe that's from the 20+ times I've dropped it from chest height face-down onto asphalt. And that thing has the original Gorilla Glass. It's tough stuff.
The GS4's screen is exceptional at exploding on the slightest of impacts, but scratch it does not. At least not in my experience.
Anyway, these "micro scratches" are things you can't even see unless the screen is off and you're holding right up to your nose. My phones are naked, forever and always. I'm raunchy like that.