I think lagalaxy8 needs somebody who's driven the previous model Y50, who now has a 2011 or newer style to chime in.
besides the obvious styling differences inside and out (you either love it or hate it, the look is starting to grow on me--I'd have to get it in black with the sports aero front fascia and lower it)
you'll be trading up to the 7 speed transmission vs the 5 speed (so mpg should be slightly improved)...still amazes me that my wife's 2012 V6 Dodge Durango can be at 2100 rpm at 80 mph and my M is at almost 3000 rpm cruising the highway.
have you thought about the hybrid? 360 combined HP seems like it should satisfy a lot of power hounds, plus waaaay better gas mileage.
BUT, you also have to deal with hard drive based navigation -gotta go to the dealer to upgrade. I like my '06 DVD-based nav....you can buy an almost new disc someone is trying to sell when they upgrade to the latest for much cheaper than buying new and of course there are some other possibilities too....
ultimately, I would probably wait to see what tweaks that Infiniti should be making to the Q70, I am hoping it's substantially different than the Q50 - It deserves to be more than just a larger/stretched out version of the Q50.