Those are some good points - especially when I stop to consider that the "VW/Audi" oil filter they install says right on it that it's rated for 2 years/ 30,000 kilometers. I think they're screwing us on this whole oil thing.
The inside "buzz" I've gotten on this issue of sludging from some VW guys is that it's oil pan capacity that they believe is creating the problem - not the oil itself. Apparently the shallow pan doesn't allow for sufficient cooling before the oil is returned to the engine. I know some guys will immediately think, "well it's because of the turbo..." - yeah okay, but it isn't the turbo coking up and dying that is the problem, it's sludge in the pan. Think about it. Seems like they could save themselves and the rest of us a lot of money if they just put a REAL oil cooler on the car (you know, like most other european car manufacturers), or cast some cooling fins into the pan. Once my warranty expires, I'm putting a Wahler oil cooler on the engine, and going back to plain old Castrol GTX. I put nearly 400k on one of my MKII's with that oil, and God knows, that engine worked one hell of a lot harder than the 1.8T in my GTI does.
My .02 - Any company that builds a little car which they later claim requires a $40 - $50 do-it-yourself oil change should be ashamed of their product, and of themselves. And you know that they are, becasue they don't even have the decency to list these specifics in the owners manual.