I'm not entirely impressed. Granted, it was my first attempt at installing, but I don't think I did a particulatly bad job. I found that the protector did affect screen responsiveness slightly - most noticeable was on the "Back" button at the bottom, which is a little hard to activate at times even with no protector. I often have to hit it 3-4 times now, or push a little harder and a little longer.
As for durability - it's NOT very durable while putting it on!! I managed to scratch it AND get a permanent fingerprint gouge and I thought I was being very careful. It was hard to install but probably gets better with practise.
I don't like the texture, it's not perfectly flat, and while I wouldn't mind the texture on the back of my phone (great for extra grip), I don't think it works well on the screen. Others describe it as an "orange-peel texture" and I think that sums it up. Also, when pushing hard (as I have to sometimes), my finger sticks to the screen and when trying to drag it moves suddenly due to the tacky (as in sticky, not cheap) feel of the material. Finally, my last gripe is that right around the edge there is a line of lint that it has picked up from my pockets. Not good.
Summing it up: good protection at the cost of usability.
Next step: After reading up some more I've just ordered some Phantom Skinz (promo code spring25 works at the moment for 25% discount, it's already cheaper than Zagg plus it appears that you get two for the price of one on all phone-protector orders). I'll update you when it arrives.
Edit: typos :(