I bought one and haven't used it a whole lot, they're as much hassle as they are convenient.
http://www.dickblick.com/products/blick-complete-airbrush-system/ This is the starter kit I got.
I learned the hard way I needed a more powerful compressor for increased PSI and CFM, thicker paint for proper coverage while painting 3d objects, and a different, larger needle for inside the airbrush to accommodate the thicker paint. So the starter kit was virtually useless for making customs. You also need high ventilation (or a small spray booth) to keep the paint mist from all ending up in your lungs. Then there's the airbrush cleanup when you're done. You'll be wishing you were painting by hand again in no time. The Iwata airbrush is great, the Iwata paints and compressor sucked. I've moved to Jacquard paints and I'm quite impressed with them.
(Sorry to be such a pessimist, hopefully someone else can share a more positive airbrush experience so you get both perspectives.)