I recently bought one of these and absolutely love the feeling of it - just like touching the glass screen of a naked iPhone! I will NEVER go back to using the plastic type of screen shields now!!
I will agree, however, that the installation IS a little tricky on these as once you let go of the shield, it's difficult to pick it back up so you kinda have to be lucky the very first time.
Don't know if its already been mentioned in this thread (haven't read all of it!) but I saw an installation video on YouTube of someone installing one of these. He basically put a piece of tape along the top edge of the Glass t.R and also one along the bottom edge of the Glass and held the shield, by the tape along the top and bottom (so he basically wasn't touching the Glass itself), and hovered over the iPhone screen, until he had the alignment correct, and then basically lowered it until he landed on the screen.
Seems like this is probably the best way to install these things.