Mine is already scratched. No idea from what.
It may be possible that it is the silicone adhesive undernearth has come loose.
In trying different cases I managed to slightly dislodge mine causing some of the adhesive to show underneath the glass. It sort of looks like scratches/small bubbles. The edges in particular have a weird looking residue on it now that looks like a cut in the glass when it is really fine.
In reality I don't see any durability issues as long as you don't move the glass once it is put on. Basically use a case that does not come over the glass and you will be fine.
Mine worked great for the past 2 weeks with the Mophie I use daily. Things started getting wonky when I began screwing around with other cases for testing. The Glass.t didn't play well with the Otterbox Defender or the Griffin Survivor. I also couldn't get any slider case on it (I tried the Incase Pro Slider, Otterbox Reflex, and IFrogz Bullfrog). It also wouldn't quite fit into the Candyshells I have. It fit, but wouldn't "lock" in.
The SP did work well with the Incase Snap, Element Comp and Vapor Pro, Otterbox Commuter, and sort of fit the Incipio DRX and NGP (though not perfect).
I guess the question most people have is if they should buy it. Personally, while it is really cool and feels great, I can't recommend it for most people. It is awesome if, and this is a big if, you can get it installed correctly. If you miss or need to move it around for a better alignment you are basically screwed from ever seeing it in all of its perfect glory. For essentially $30 it isn't worth it since you are probably going to not get a perfect install. I personally have a small piece of lint underneath. Luckily it isn't on the usable screen portion so I'm ok with it, but if it was on the viewable screen I'm sure it would be really annoying. It wasn't hard to actually get it on but getting it perfect is trying and in the end I failed.
I would recommend either the PS Crystal since it is half the price of this guy and comes with multiple SPs in the box. Sticking with SGP, the higher end one (the Ultimate Class) is good but not $27 good like some people are leading it on to be. It feels identical to their other crystal ones which are half the price. If you are going to spend the $27 on the Ultimate class, which only gets you one as well, then you should just get the Glas.t and hope for the best on the install. I would get the HD Optics or the Oleophobic one from SGP before the Ultimate Class.
I find it kind of funny that the "reviewers" are all praising the Ultimate Class when in reality is identical to SGPs other one (the HD Optics) for essentially double the price. I had one of the HD Optics and one of the Ultimate Class on two phones side by side and I honestly couldn't tell the difference except for the odd thickness of the Ultimare one. Looked and felt identical otherwise. Not sure why people are trying to make the Ultimate Class out to be better than it really is since it really doesn't seem any more or less durable than the standard ones, just oddly thick. It still scratched when I put it in my pocket with my keys, just like the standard one so sure why it is marked at a premium due to it's "hardness" as it won't protect your screen any more or less than the HD Optics one for $15.
In reality, since people got them for free for review they are probably a little starstruck at their new stuff just like they are with those stupid Phosphor watches (which are overpriced and cheaply made by the way). Full disclosure time: I got all of mine for free too. I just don't forget that these things cost money when I make a statement/review about them.
End rant