Hi David,
I started with (and still have) a $150 dollar airbrush, use it quite happily as an all rounder tool.
Lays down primer, first coats, does some shading. Lines as fine as 3 -4 mm.
Not quite as precise or as sharp as I want it to be some days, I reckon it's the guy holding the airbrush, not the air brush itself that occasionally gives not so great results.
Brand is a Sparmax, DH-103, double action (way better to use then a single action!)
This will serve me for many years (barring accident) until I can justify shelling out for a better model.
As for results, search for Pepa, she does some great stuff with an airbrush!
Cheers