I recently purchased a G80 over a much more expensive A6. After about two weeks with the car, I agree with one of the previous posters that the ride is not quite as good as the A6. Part of this is because I got a G80 Ultimate and it has the bigger
rims/smaller tires. Another part of this is that the A6 has an air suspension. Even with the A6 sport suspension, the air ride is better at smoothing the smaller bumps.
I will also note, unfortunately, that the A6 is probably more nimble. Or at least I am still gaining confidence in the G80. I previously had a S4, so what do you expect. I mention this because on my first trip down the interstate, an RV one car up from me had a blowout and I was unable to avoid the tire. In my S4, I have no doubt that I would have been able to dodge the tire, but I took it directly on the passenger side of the front clip. So I am bringing my brand new G80 (up to 800 on the odo after that road trip) to the dealer tomorrow to make sure there is no other damage. I hear a slight higher-pitched (belt?) noise that increases with RPM (not the engine) that I didn't have before so I want t get it checked out.
ANYWAY, I do think the G80 is fabulous and a "smart buy" but a fully loaded A6 drives better if you don't care about the extra $15000+ to get loaded 3.0T version.