My wife and I both have Fascinates. She has the Zag screen protector and I do not.
We both have a soft silicone cover over the back. After 5 months I can tell you this.
1. My screen in brighter, and easier to read.
2. My screen looks better.
3. My screen is more touch sensitive.
I believe I did an excellent job applying the screen protector but in the end you can still tell you have one on. If I took off her screen protector and cleaned up the screen and compared the screens side by side you could'nt tell which one had it on. In other words do waste your money on screen protectors for this phone, they really don't need one unless you totally abuse your phone. As for finger prints and smuges no screen protector is going to stop this, in fact I think they enhance the problem. A quick one over with a soft cloth and my phone looks brand new.