Hey man - I had a 2001 A4 1.8TQ for a year before I traded it in for my first e90 (second best decision I made in my life so far, first best decision I made was recently trading in my e90 for a newer e92!
Anyway - back to the Audi...within my 1 year of ownership (I was the second owner), it was in the shop 3 times. First 2 experiences related to the auto steptronic tranny - would not shift up or down, quoted me a couple grand to fix. 3rd time, I had an oil leak in the driveway, so I took it in to get checked out. Turned out I had a huge crack in my oil tank, and there was oil everywhere. Turbo began sounding a little odd around this time too. Traded it in shortly-thereafter.
My stomach is starting to turn just thinking about my ownership with that car. I couldn't wait to get rid of it. And I've had nothing but great experiences with my e90 and e92.
My only recommendation is to get the car fully inspected before buying (something I failed to do), and buy at your own risk. Used cars are always a gamble, especially if you aren't looking at any newer, certified pre owned audis.