It looks like most major publications in the US have their first reviews out:
-
Car&Driver
-
Motor Trend
-
Jalopnik
I've test driven the Stinger GT, and I came out relatively impressed by it. It's not a sports car, but as a GT car, it's quite a bargain for what it offers. It's still too soft to compare against the 3/4er or A4/5 though (and my opinion of the F30 isn't very high to begin with).
All these reviews state that the G70 is lighter/smaller and exhibits less body roll, and ultimately is a better driver's car.
I am not sure if the G70 is my cup of tea, but I will be lining up to test drive it for sure.