I have been doing this style for almost 20 years now. Never once have had a customer complain, or question the line. I have, in fact, taught several customers how to do it, as they commented that the lines look great. It looks good in big or small rooms, hallways, wherever.
I use a Wooster 3" sash brush. I just cut in the wall, and gradually move the brush closer and closer until it hits the ceiling ever so slightly, and keep moving down the wall. Its important that the overlap is tiny and consistent.
I couldn't really find any jobsite pics where I took a pic of the line close up, so I just went into my son's room that I painted myself 2 years ago. It might be kinda hard to see, as he was asleep in there, and I had a night light to deal with, so I used the flash.
This is an extreme close-up of the line:
Here is what it looks like when you take one step back. This is probably the closest a customer will ever get, unless they are bumping their nose on the wall:
Another view from the same distance:
Step back a couple feet, and look at it from a normal viewing angle, and it looks tight and sharp:
I'll try to take some pics in there tomorrow in the normal light.