I'll start off with the good stuff, the real nitty gritty. Kazutoshi Mizuno of Nissan claims a 45 horsepower increase, bringing the total to 530, and a slight torque increase. Upgraded boost ensures that the new GT-R can hit 60mph from 0 in 2.83 seconds.
Other changes (or upgrades) come in more subtle forms. Nissan has created better sound deadening, more suspension tuning has taken place to help reduce under-steer, and some more detailed computer tuning which I won't get into.
The GT-R has become a prominent supercar, most comparable to the Porsche 911 turbo (though far less tame), and with a price tag of around $100,000 it's interesting why people buy vehicles twice its price.