Vin - The ride might have been a tad softer than our B6 S4, as I recall, but I've never ridden in ANY Audi of recent build that didn't have perfectly refined ride manners. I have a friend who has a Fly Yellow RS6 (it's hideous and hilarious and makes a real statement, but hey, you only go through once). Even with 19" wheels it rode very nicely with no harshness.
In terms of the 340hp corporate VAG V8, it's a very reliable piece, as is the Tip transmission. The service manager where I dealt told me it was among VAG's most reliable and dependable units. Granted, I was asking about the A6 4.2 (300hp at that time) and not the S6, but this engine is not really stressed even at 340hp. Check out
www.audiworld.com for a wealth of knowledge, and good luck!
Mike