I have been almost exclusively using Benjamin Moore for quite a few months now. It is definitely a high end finish. I can't think of a specific time when I have had to put yellow on blue yet though.
I may have done, I have used alot of colours. Most cover very well in 2, I have found a couple that didn't though. They only guarantee 2 coat coverage with the Aura range and I do use others in the range too, which usually cover just as well.
When using the ceiling paint you can easily achieve such a floorless finish that I have been accused of spraying the paint on several occasions!