Recently took my car into the dealership as the result of it making a weird noise from the front or engine bay..... Turned out it was the front crankshaft seal, which the dealership indicated a bulletin came out on from GM. The technician working on my Z06 couldn't help but to notice the catch can system, which caught allot of attention from some of the other technicians in the shop. According to the service writer I was working with, he indicated all the technicians were quite impressed with it after studying it. They could see no reason it would cause any warranty issues in the future because it wouldn't cause any future failure of any OEM components.
As far as pictures of ports and valve pocket areas being clean and free of any valve coking on the backsides of valves is concerned...... Not saying anyone would be deceptive to make an argument opposing catch cans, or not be completely truthful, but so much opposition and controversy connected with this topic causes me to wonder.... As stated before, I've been more concerned with the contamination issue more than the valve coking this entire time and it's affects on performance. Everyone saw what I pulled from my catch can earlier, which surprised me as well, but as stated before while participating in spirited driving on mountain curves I operate in "Manual" mode with my A8 and decelerate by dropping down gears and using the brakes quite a bit, so vacuum is high during those periods.
These catch cans represent an insurance policy in these earlier stages and they've been proven to be effective in other application with direct fuel injection as Busa Dave has indicated, so for those skeptical of catch cans, by all means DON'T DO IT and leave everything as is. As far as attempting to tell others they're wrong because you personally don't agree for the sake of argument, well what can I say... Keep doing what you're doing or not doing. That's your right as an individual, but to try to convince others to change to your way of thinking based on your background history on this topic...... Well, what can possibly be said.