Having owned a G35 Coupe for several years I agree it has aged very well. It was fun to drive, reliable, and costs to maintain it were reasonable. With the six speed and the Brembos it was both a good canyon carver as well as a cruiser. Fuel economy wasnt the best though. Comparing the styling of a new vehicle with their higher belt lines means you won't get that type of styling anymore (just like you won't see cars like the original NSX or RX7 twin turbo anymore either). And likewise, the new Buick is a looker but comparing a production car to a concept car is unfair...things are definitely going to change when it rolls out in production mode.
I am definitely happy that the G...err Q60 has the new engines though. The VQS were getting long in the tooth and the new engines look very promising. I'm hoping that the they are mod friendly and find their way into other Nissan/Infiniti vehicles like the Z , the QX50/ 70 !and maybe even the Maxima. The better fuel economy (I hope) is also a bonus.