An Audi, along with any German luxury sedan (Audi, BMW, Mercedes) is a great car to own when you can afford it. if you can properly maintain an Audi, it will take care of you. Audis have exceptional all wheel drive technology (which led them to dominate in rally during their earlier years), they also have more efficient engines (which led the to dominate in the 24 hours of Le Mans races) they also have superior chassis technology that makes them light and strong which makes them better than Mercedes larger heavier chassis (i don't include BMW in there because they have a sporting pedigree that is hard to beat)
for practical reasons, an Audi is very safe, the amazing 4 wheel drive will keep you out of accidents and if you still get in one, the aluminum space frame chassis will keep you safe when all hell breaks loose. maintenance and insurance will be higher than regular cars but they don't offer the mechanical advantages that only an Audi can provide. if you really value safety, an Audi is the way to go. The Audi A4's active safety components won it the 'Top Safety Pick For 2007' award from the North-American Insurance Institute for Highway Safety. In IIHS crash testing, the A4 received the highest score possible of "Good" in both the frontal-offset and side-impact categories.
edit 01: Audis, along with the other 2 German luxury car makers are good even when used, you don't need to buy a new one to be good. in fact, a 2002/2003 entry level German luxury sedan is comparable and in some places exceeds the quality and features of a brand new (2012/2013) regular car. this is especially true for the interior and mechanical safety features (electronic safety features like traction control and ABS with brake force distribution are standard on most cars but new regular cars still don't have advanced chassis and all wheel drive technology as standard)
edit 02: it also doesn't matter if you drive a nice car because the one person that needs to be happy with a car is you. if there was no one on earth to impress but you could drive whatever car you wanted it would still be a good one would it not? while the social factor of driving a luxury car is present and depending on your personality its also desirable, remember that you don't have to be a show off to drive a good car. (if it were up to me i'd drive a mclaren super car even if the rest of the world hated me for it just because i would enjoy the car) others don't need to enjoy what i have so why should i let it bother me?