Hi Will, I have had my Grex XT for a couple of months, and have been happy with it so far. I have shot testors model master acrylic through it as well as Sig dope. It has very fine atomization, when I painted the cockpit of my new Dreadnought with it I joked with Eric that it put paint down one atomic diameter at a time. This means good surface prep is more important than ever.
Needle removal is easy, internal polishing looks good, I have not really tested the fine line abilities of the brush yet, although I suspect they might be down near the 1/8th inch realm with the tip I have. Not sure I would want to paint a whole stunter with it though, and there would be *no way* to hose down a wet final coat of clear.
Really, one of the 20 buck single action suction feed badgers works well for most stunt plane trim work. I got my Grex for the plastic models. The picture below is the first model I tried with the Grex...