You should test drive the 370Z to see how you think it feels. One thing I miss from the DE is the low end response. With the VHR, you have to rev it past 3k. If you spend most of the time revving past 3k, more power to you!
I've only been in an '04 G Coupe, and I was never a fan of the interior. The G37 and 370Z definitely has a nice interior, and I have no gripes about it after 2 years.
Transmission-wise, I've not had any major issues with my transmission after 20k miles. It rarely grinds, and the shift effort is so much nicer. My 350Z transmission was replaced in '06. It was nice for the first 3 months, and started progressively failing. It liked to grind 2nd and 3rd, and the shift effort hurts my wrist.
If the 370Z was the car I had from the beginning in '03, I would not trade it in. It's a keeper.