I was lucky enough to take a check ride in a pre-production G35 today. It had a detuned motor about 20 ponies shy of the production car (240 vs. 260hp) but still had a lot of power and exceptional handling. The car has an exceptionally smooth ride but handled on par or better than any sports sedan I have been in in recent history. The transmission has a steptronic feature that worked well, it shifts like a luxury car if left in drive but will redline in manual mode and shifts very smoothly even at peak power. This car will be very fast and a very capable car in the canyons. I will be very interested to see how it performs vs. the IS, 330 crowd.
There are some dislikes. The seats do not offer as much support as they should for the level of performance the car offers. The actual shifting mechanism has to long of a throw to shift manually. The interior is nice but not on par with BMW or Audi a bit on the Nissan side. The steering feel is very light and the brakes are a bit touchy. In other words it feels like it will handle as well as a German car but doesn't feel like one, big surprise.
I think Infiniti has a winner. The cars aesthetics are subjective, though I like the conservative stealth approach. It will some ace on the street. Cool Xenon and LED brake lights. BIG car 112 wheelbase, roomy back seat (legroom). Decent tunes. Cool pop up Nav screen.