I recently had Best Buy install an Invisible Screen on my phone. Prior to that I had the VZW screen protector and no screen protector. After the change from VZW to bare screen I notice a feeling difference, and again once the IS was installed. In each case, I only noticed it that first time using it. After a few used, I couldn't tell the difference...and the sensitivity has been the same throughout.
As far as screen protector scratches? That's why the VZW protector came off. I haven't yet scratched the Zagg, but I'm guessing it's only a matter of time! It funny, I never used screen protectors on my Storm, and that screen never scratched. I wonder why I'm worried about it now.
Steve in CT