Pages from some 150,000 "trusted domains" will be rendered using the IE engine with additional security features and the rest will render using the Gecko engine and it's "hands off the OS" approach.
This sounds very fishy to me, or at least highly undesirable. I knew you could choose to use the IE rendering engine in NN 8, but I really don't like the idea of it being turned on and off automatically just because someone, who may or may not know their business, has decided to "trust" a particular website.
I use Gecko-based browsers for a reason. I don't want Gecko "turned off" unless I do it manually.