Well.. I test drove a 2008 Audi 2.0T S-Line Quattro today - one of the shortest test drives I have had. The vibration of the steering wheel left my hands somewhat numb for a good 30 mins after the drive, the road noise was high and the ride was hard (ok - S-Line, sport tuned suspension... I can appreciate it being a firm ride, but not hard) and frankly, a Jetta TDI is quieter and shifts smoother than this 2.0T.
A friend has a 2003 A6 and the difference between it and this 2008 A4 is significant - the older A6 beats the 08 A4 hands down... but enough about my Audi experience (not a bash of Audi, simply an observation from someone who seriously considered both the 08 A4 and the 09 328ix.)
I then drove the BMW - and it was precisely how I imagined a high end car to be - smooth engine and ride, very little road noise and a gorgeous interior (tan): it was brilliant. Plenty of power, COMFY seats, sleek and sexy looks.. it is exactly what I am looking for in a vehicle.
The dealer has a 200k unlimited time frame warranty (never heard of that!) and I'll be checking it out before I sign anything, but aside from that the car still has a year of factory warranty as well... so I'm 99% sure I'll pull the trigger (depends on what the ext. warranty does/not cover). I'm excited and won't sleep much tonight!