I had an invisible shield on my iPhone for about 16 hours. Took it off because even though it was on the phone without having a color tint to it it kept getting little "nicks" I would say and actually dust got under it while it was on! Went to the local mall and they have a ghost armor place, had them do a full body coverage, with the back panel having a matte finish. Love the way it feels and looks!
I used to have Invisible Shield on my 3Gs but found it quite 'sticky' and had a feint orange peel effect no matter how I fitted it. I found "Phantom Skinz" protector to be first-class. Very smooth and used it for nearly 12 months now and no sign of discolouration.