There doesnt seem to be a lot of info about Scratch Shield, mainly because our main source of info - the US - dont use it much any more, litterally only on the GTR I beleive - the G37S didnt have it after the first model year and Nissan never put it on the 370z out there. Over here, Infiniti do use it on the G37 and Nissan have it on 370z and GTR. It only comes on metallics and pearls.
From what I have read, it is an extra resin in the clearcoat which allows the clearcoat to expand slightly. This has restricted movement, so will only cover small scratches to the clearcoat only, if you go through the clearcoat, it wont do anything. Its designed for swirls and very light scratches. Heat activates it (Infiniti confirmed to me that they use heatguns on it), and it pretty much only works once due to the spreading effect having limited movement.
Having seen multiple details on it, some have said the paint is a pain as it warms up, swirls go away, it cools and they come back. Others have had more success and have not had this problem, my guess being they use a more agressive compound and generate less heat so cut straight through the clearcoat. Those that work it more, warm it up and get the weird results. Mostly I think going by DW forums, its not hard to deal with.