Did you put the Zagg shield over the 3GS before playing with it at all? Can you give a comparison of the feeling between the two?
Honestly, I wanted the Zagg on my phone the second it was out of the box, so I had the Best Buy guy put it on when activating it. However, when I returned my 3g, I took off the Zagg, and played with the screen. There is a difference in feeling, but I like the Zagg more. Its more tactile.
Here is my best example. My friend who loves iPhones, was playing with my 3Gs at my apartment a few days ago. He loved the 3g, but wanted to play with my 3Gs. He remarked "did they change the screen? It feels so much nicer!" I responded saying that it had a screen protector on it. He was like "really? I couldn't tell."