I suspect a big part of the problem with 1.8T's, is that for some crazy reason Audi specify Semi-Synth oil for them, upto switching to longlife and AVS in 2000.
And while i would imagine that if you stick to the 8000mile service interval on that semi-synth for the most part you'll be fine, people tend to miss services, stretch the intervals out, use low quality oil (perhaps even unintentionally by an ignorant garage) etc. With the engine being turbocharged, its a LOT harder on the oil than a similar power N/A engine, and it really should have been run on synthetic oil from new. It doesnt take much to push that overstressed semi-synth over the edge and it turns to treacle.
When we baught our car, i wasnt really aware of the issues, and the oil that came out on the first change was like treacle. I immediately ran flushing oil thru it, and then changed the oil every 5k thereafter. The bad oil had taken its toll though, and the oil pressure was low. However because i actually looked after it, it ran with low oil pressure for 40k and nearly 2 years of driving. I should probably have changed the pump and it would have been fine again, but time/money constraints meant i kept putting it off, and by the time i was ready to fix it, i ended up fitting another engine instead.
The reason i dont run super special branded oil, is i figure Motorfactors spec 5w40synth changed every 5k, is better for the engine than mobil1 changed every 10k, and because the factors stuff is half the price, it costs the same at the end of the day.