I never hear anyone mention Tamiya airbrushes here. Are they not popular outside of Japan?
I've been using their superb HG Trigger airbrush for the last five years or so, and it was a gem from the get go. I had used a really cheap Testers piece of junk prior to that (only good for laying down base coats or primer, and not that much better than spray cans!), so perhaps I cannot offer a qualified opinion as the how the Tamiya holds up to other ABs, but I do know that this AB does everything I need it to do, with absolute consistency, and with no problems whatsoever. As my techinique improved (and improves!) I discovered just how versatile this AB is.
It's very comfortable to use (I like the trigger design so much more than the push-rock buttons on other dual-action ABs. Maybe because my hands are the size of a bunch of bananas!), easy to clean, and very easy to adjust.
Until I run into something it can't do, I don't foresee ever buying another airbrush.