nate,
The Passat seems to be a testbed for features that are going to go into other VW cars. Also, VW seems to sometimes not uprate the parts enough the first time around for the bigger car.
That said, I took a 1995 Passat from 70k to 156k before selling it, and apart from stuff that I broke myself doing silly things like driving over a curb, the non-maintinance items I had to replace were as follows: one EGR temperature sensor, one crank position sensor, one door latch, a thermostat, the load reduction relay, the secondary electric water pump, and a couple of gaskets and little clips here and there. I'm not counting things like brakes, struts, tires, so on, which wear out on every car. Actually, the stuff like brakes have done well: I put two sets on, but the second set is still more than half left, and I did the clutch at 150k but found out I didn't need to once I got it apart. I took it apart because the timing chain was getting noisy, and though I'm glad I did that, I didn't really need to once I got in there
- it was in OK enough shape for much more service, but since I had it apart I replaced the guides and chain anyway. The car is still driving around and hasn't needed anything else yet. Of course, if I had paid a shop to do these things I probably would have a bad opinion of the car, as I would have spent much on labor to fix little fiddly things that didn't need parts, or were an hour of work and a 15 cent part. An example: on the B4 platform there is a little pin in the door handles that slowly wanders out. You can pop the door handles out, grease them, and drift the pin back in every year or two, or you can do like I do and drill the pin out, then replace it with a screw and nut. It's annoying and takes a little bit of time to do, but it's not actually expensive to fix. Of course, I didn't need to do it the first time until 100k were on the clock, so if you tend to keep cars for less than that it might have never been an issue.
Lately with VWs, the lineup seems to be pretty solid mechanically. For instance, the VR6 engine has the bugs all worked out, the 1.8T seems fantastic for a turbo motor, the 2.0 is basically bulletproof if a bit of an oil consumer at this point, and the pre-2003 TDI has a short list of well known faults. The 2.5 FSI is still an unknown quantity and I might be a bit leery of it; thankfully the FSI system has gotten a couple of years workout in Europe, but it still is relatively new. New VW injection techniques aren't inherently bad, but even the (awful) dealers might not know how to troubleshoot them well yet if they go wrong, as it takes a certain amount of Zen to troubleshoot VW systems.
-Keith