Wow - Thanks. I was not aware of this, although my salesperson did mention that it was due for a redesign. 440 GC it is, then, if I go BMW.
I think you're both wrong.
Plain "TACC" will only keep pace with the car in front of you, but at certain higher speeds and will not work in stop & go traffic. Traffic Jam Assist (like BMW's "Stop & Go") will adjust speeds at higher speeds like TACC but will also work in stop & go traffic.
I do NOT think Audi's Traffic Jam Assist steers for you. I mean, it might with Lane Departure... but you'd be weaving back and forth like a drunk person.
The loaded A4 Prestige my dealer guy wants me to consider has Traffic Jam Assist. If I give it a test drive, I will definitely see if I can do it where/when there is some traffic to try this out.
Driver assistance systems
and
Cause and effect
EDIT: Reading at those links more thoroughly.... Audi also (separately?) has something called Adaptive Cruise Assist, which DOES read lane markings and keep you to the center of the lane.