I own a 2003 Passat with 190+k on it. I love the car, but I didn't pay very much for it. I have the 2.8L 30V V6 and it is LOVELY to drive. I think mine is fairly loaded (short of the W8 and AWD), so the stereo, seats, moonroof, etc are all awesome. I really enjoyed driving that car on a 5.5 hour trip.
But, it does have its flaws. You have to put it into 'service position' to get at most anything in the engine compartment. Sure, that only takes about 45 minutes, but it can be a hassle when you just need to change the alternator, etc... Also, a few check engine light hassles every now and then. Nothing major for me, but it hasn't been a care free car. Right now, I'm aggravated that the heat is to hot unless I set it on 64*. Also, I'm never really able to get the intermittent wipers at the perfect speed. Ohh yeah, and I need to have my ABS module rebuilt (around $150 plus $100 labor).
I will say that the engine and transmission are awesome. Really a nice combination. Plenty of power and acceleration while being smooth and getting decent gas mileage. I tend to get around 20MPG for mostly stop and go driving with a bit of a lead foot. I have the 5-speed automatic. I don't know if the 5-speed manual will get you any significantly better fuel mileage.
I have heard that the turbo four cylinder engines are good, but not quite as reliable as the V6's. The W8's are supposed to be awesome for power, but I don't know how expensive they are to maintain. I have heard that the AWD systems are very robust and don't need a lot if any maintenance.