The most comfortable car we've ever owned is my wife's M-B E320. It's
just super in every way - smooth, quiet, powerful and great seats.
Consumer Reports rated it as one of the best cars they've ever driven.
My wife had one for a company car for a while. She liked it, but I didn't. Too soft and no fun to drive. Her favorite was the Lexus LS460. I hated driving it, but it was nice to be a passenger, especially on a long trip.
She had an A6 Quattro, and that's what introduced me to them. I've had two since then, currently still driving the second one. Love them. Comfortable, sporty, quick, and sure-footed with the quattro system.
How's the service availability? That's one thing I learned about having
some of the nicer, performance orientated, foreign made cars.
For example, the BMW M5 called for special oil that was only available
at the BMW dealership.
Wasn't a big deal since oil changes were covered but if you were
traveling and needed a quart (the M5 *did* use some oil, especially
during break in) you would have to hunt for a BMW service place.
The other thing I disliked about the BMW M5 was the very specific and
long break in procedure. RPM was limited for the first 1,200 or 1,500
miles and then a gradual allowance to start "getting on it" until you
had about 3,000 miles on it. The computer in the car recorded any
violations of the procedure so, in the event of a problem, they could
point their finger at you. Biggest problem for me was I had to go
through this twice. They took back the first M5 I had due to many
computer software problems. They assured me that the second one (same
year but built 7 months later) had all the issues sorted out. They lied.