I just bought my 2001 A4 Audi Quattro and I am content with the car but th eonly thing that is troubling me is the Heater. Only cold air seems to come out of the vents even with the car being driven and started properly. It is very cold at the moment and I am suffering my having to dress extra layers of clothes just to drive my car.

had my car since brand new on january 2002.
2002/2003/2004 were covered under warranty.
My repair bills for 2005- $2592.00, 2006- $3906.00, 2007 $2660.00, 2008 $1557.00, 2009 $2407.00
TOTAL $ 13106.00/ 246492 kms = 5.3 cents per KM

This is double the recommended average br CAA Canada.
Also my reapirs woudl have been much higher if I let AUDI dealer do this.

I have been driving my 2001 A4 Quattro Avant V6 2.8 for about 4 or 5 months. Overall I think it is a good vehicle. It is my first Audi, and I bought it used for a good price because it is older and higher mileage.
So basically, I am speaking from the perspective of an aging Audi, for potential used car buyers.

Body and interior have several luxury features including an excellent sound system, moon roof, and layout. Complaints here include noisy, cheap-feeling plastics, and electronic glitches. For example, in cold weather, the moon roof will automatically shut on its own if I have it tilted. I open it again, stays open about 5-10min shuts again. If I want to open it, I just have to slide it back instead of tilt. Cup holders, as mentioned in reviews below, are ridiculous. You can only fit something the size of a can in there, and location is not very handy. The electronic display messes up frequently making the information you rely on, such as current mpg, indecipherable. Also the warning system needs some kind of snooze to it. In mine, a water pump in the washer reservoir is cracked, so my fluid is always low. Instead of being able to read radio/stereo info on my dash, I have to watch the fountain animation reminding me to fill my fluid, constantly.
I find the brakes to be a bit lacking, but like most things in this car, it depends on the situation. Stopping distance seems to improve if you are at higher speeds. I think this may related to the engine assisted ABS where, somehow, energy from the engine is transferred to your ABS system. Audis make adjustments for drivers all the time in order to improve performance, but this can be a burden for those of us who expect machines to respond consistently. I highly recommend you put an Audi through all of its paces at test drive to see it it suits you.
Drive train is not too bad. My transmission feels sluggish from a stop, so I will often switch to manual shift to to get moving a little more efficiently. It is wonderful to have that option. If the car is getting older, like mine, it is difficult to diagnose the problem. There is no dipstick to check the current state of your fluid, and a complete fluid change kit with filter runs around $120, not too bad. However handling and power are both really nice, and make this car a great cruiser on trips, or slaloming around corners to get the kids from school. There are also many ways in which this car will leak oil, which is apparently common as they get older, and changing seals can get expensive.
When I bought the car, the blinker relay needed replaced, but it solved the lighting issues that came with the car for only around $35 (replacing it myself). In a non-HID system like mine, the headlights seem a little weak, but replacement bulbs are cheap and easy to find, and aftermarket light kits are everywhere.
Apart from the common leaks and expensive repair costs, the engine seems very sound, and I think that Audi engineers really nailed it. Do not expect good gas mileage in the older Audis (not sure how the new 6 cylinders fair though), but performance is far far better than your common econo-driver.
Exhaust is pretty blah in these cars, no sound, no flash of detail. Designers apparently took an out-of-sight-out-of-mind attitude toward the exhaust system. Upgrading one may yield better performance and sound. I'd also guess that emissions on older Audis were not a primary concern, so be careful.
Heat has not worked in this car since I bought it because the engineers designed the heater coil to filter the coolant system. This is really frustrating considering the heater coil lies under all of the dash components and center console, all of this stuff has to get ripped out to replace the coil when it clogs (and it will clog). Most people do a back-flush of their heater coils which should remove the sludge that builds up, but regular replacement of the "lifetime" coolant will probably help prevent the problem in your Audi.
Suspension is above average in these cars, the ride feels great, though a bit noisy. In mine, I discovered a coilover (spring) broke in the rear of the car and the noise was considerable because it threw my shock out of whack. I have talked to mechanics and other owners who say that over time the suspension parts get noisy, and wheel bearings go bad often, causing road noise. Generally, these replacement parts are no more expensive than other cars, and if you find a trustworthy mechanic or do it yourself, replacement shouldn't be too bad either.

I wanted to be as detailed as possible to help you be an informed buyer if interested. I wouldn't recommned an Audi to someone on a very fixed income, or who could not afford to have it serviced regularly.
If you want to own a luxury car to be worry/hassle free while continuing to be an excellent performer, look elsewhere.
In my opinion, Audis are cars made for people who are willing to spend the money needed for regular maintenance and servicing (which will be considerable) in order to keep an excellent performer performing excellently.

im 19 first car i bought for myself for living in new york its great for its size. love how quik it is, but not enough room to see its true patential=( only have 41k on her.no serious issues just the pricey air pump that varies from $275 to $400. other than parts being to much i have no complants absolutly love the after market choices!!

I love the Car (A4 Avant 3.0). Just bought it so time will tell. So far it's exactly what I was hoping for in an Audi. Unfortunately I have to get the timing belt service done soon. Very pricey on the 6 cylinder.

I love my Audi A4. With Quattro you can gun it through turns and live to brag about it to your friends. After owning the car for 3 years I still love taking a 35mph turn at 65 and laughing confidently as the tires grab the road and whip you forward.

If I had not have had a extended warranty on this car I would have been forking out a lot of cash to the local dealership.
Second Audi and not to sure if there will be a third!

Overall a good car. Bit pricey with all the whistles and bells but I do enjoy them all. Highlights are the adaptive HID headlights. They turn and point when you turn the steering wheel. Quattro makes the car drive like it is on rails in all weather conditions but it does require the pricey high performance tires. They removed the seat memory and made it an option. Should be included in the technology and trim package I purchased.

Problem free until now. Has right rear brake caliper frozen. Replacing it, as of now.

Excellent car - rock solid so far. 120k. Cam seals needed replacing at about 60k. This is a very costly repair (~$3k) and is apparently very common. Other than that, things have been great.

OEM Brake pads create a ton of black dust. Aftermarket pads are far better in all respects.

Body has held up very well for 120k, still very solid - no rattles.

Exhaust system went at 110k. Price to replace pipes and muffler was nothing short of outrageous $1000-1500 no matter where I shopped. Purchased APR stainless performance exhaust for $950 and had it installed at local muffler shop for $100. Sounds slightly (5-10%) louder, but my wife thinks its just fine.

A/C is not the most powerful, especially when idling.

I contintue to enjoy this car every day. I am midway through my second 100k mile chunk and still have no serious problems with the car. Occasionally there is something that needs replacement but it is what I would expect to need replacement at such a high milage. The only reason I rated the interior lower was because the cup holder options in the earlier model years of the B5 (97-2001) A4's are pretty pathetic. I think Audi was going for some artistic note to hold your drinks but the only art is the Jackson Pollock coffee stain you get on your pants when going around turns. Otherwise the interior is great.

The exhaust and emissions are not the greatest but this is not exactly a light car such as a civic either.

One thing I like to point out about Audi cars is the incredible response between the steering wheel and the direction of the car. To put it in comparison, when you drive most american cars, there is some slushy feeling when steering in car. Audi's have immediate response when you want to make the finest detail change in the direction of the car.

This is a well made car with plenty of room to carry things (even the sedan), an ability to handle any terrain including snow, and plenty of power for a luxury sport sedan.

I recommend A4's to any and all of my friends who consider buying them.

I love this car. It's the perfect size for city driving (parallel parking is a breeze) and the 4WD takes you to Tahoe in most any conditions. Living in San Francisco, the Quattro is a must - it gives me an extra sense of security on those many rainy days. I opted for the 3.2, 6 cylinder option which gets me on the freeway (and up mountain roads) in no time. I have developed an addiction to the GPS and satellite radio as well. The only negative is that we can barely fit 3 kids (in car seats) in the back, definitely not a car for an expanding family. I thoroughly recommend an Audi.