I searched here and saw conflicting reports. I would like to know if there is currently a Giottos screen protector correctly sized to fit the D800 screen. I have never used one, but thinking of trying it.
I use the entire screen for composing landscapes in live view, and do not want something that blocks any of the LCD image.
My experience is that the Giottos are far more delicate than the GGS. Every Giottos screen that I have had (3 or4) have cracked, chipped or scratched. I've had a similar number of GGS screens and none has had any damage. Perhaps it is just bad luck, but I see a trend.
In addition, the SP8304L, which I bought with my D800, covers part of the screen with the wide border (as noted by Dave) and is not as good of a fit. It is really a Canon sized cover.
I will say that the Giottos screens are slightly for viewing than the GGS.