Revision B diverter valve failed. Caused boost to leak, giving the car poor performance. $150 Aus and an hour installing the revision D diverter valve (a fiddly job but not complicated).
Boot latch stopped working, boot would not close. Replaced.
The remote locking stopped working, read the cars owner manual and easily re-programmed the key.
Main key remote stopped working. Had to get replaced.
Coil pack closest to windscreen failed, caused the car to run on 3 cylinders (gave me a fright, thought the gearbox had a fault!). Apparently this fails often as it is closest to the windscreen and allows water to get into it. Cost $150 Aus to fix.
The above are small problems, most of which I have learned are very common after searching numerous Audi Forums.
The plastic clip for the middle arm rest is broken. Every second hand Audi I have driven already had this broken so it is a common fault.
What I like:
The exterior shape of the machine.
Very low but comfortable sports suspension. Ride quality is excellent for all driving situations. 3-4 hour trips do not destroy your back like the Japanese cars I'd owned did!
Automatic gearbox is very smooth and most changes you cannot feel. Has paddle shifters on the wheel for twisty roads. If you want this car for speed, I suggest the manual gearbox as it accelerates much faster.
The amount of torque at low RPM is fantastic.
Fuel economy. Strictly town driving I get about 10-12 litres per 100 kilometres, highway I get approx 7.5-8 litres per 100 kilometres. All depends on the driving style.
Excellent handling. Does not lose grip in the dry and rarely ever loses grip in the rain. Steering and all wheel drive system much better than Subaru WRX and Liberty's. Tyres are wearing almost perfectly even due to rotation. Would easily out brake any other car in it's class, they are the size of a BMW X5's!
Cabin is strictly functional, highly practical. I really like the look of it, mine was optioned with silver inserts rather than woodgrain. Boot is massive and the seats fold down, which is very handy. I also love the twist control for the sunroof instead of holding a button. Massive glove compartment.
I recently had the tuning company GIAC install their ECU re-flash, the engine now pulls much harder. Apparently has lifted the power to approx 189kw and 395nm due to increased boost settings. Now accelerates faster than the 3 litre 6 cylinder A4.
Most people seem to like Audi, many people find Mercedes or BMW to be too flashy, despite having similar specs and being similar in price.
The fact I bought this second hand cheaper than a brand new luxury Honda or Nissan sedan. The brand new Japanese luxury cars do not even come close as far as product finish and performance.
What I do not like:
Sound system. It is excellent factory system with the subwoofer, do not get me wrong, but it does not play MP3. What were they thinking?
The arm rest on the drivers side door is low and the window is high so you cannot rest your arm easily.
Overall a great car. I would love to get my hands on an Audi RS4 or Audi R8 and see what they can do if this car is any indication!