I had the previous GS300, the V-6. I would totally agree about a fast Lincoln, though more comfortable. I didn't get the GS430 last time because the V-8 held little appeal, as the car was a "faster Lincoln".
Even my SC is less "fun" than it looks.
The 06 GS is not softer than the 2002-05 models. It is smoother, but if you want to get out and go, you'll feel the road. It's not that "stadium seat with a rocket engine" feeling you get from BMW, but you know you're driving and there is a serious beast under the hood.
To be honest I am not terribly experienced with BMW's, but a good friend of mine has a 330CI and it is a fun car.