Steve
I've not used one, but have read and heard they are generally considered "knock off" products, possibly made as copies of other brands, likely Asian.
Tales have been both good and bad, kind of pay your money and take your chance. Some folks have had great results, others say they're not worth taking home. Case by case I guess.
A good website to check out for detailed info is: Don's Airbrush. Plenty of good information regarding types, brands and quality. That should give you enough to go on.
For what it's worth, plenty of good quality, name brand airbrushes available through the dealers, I use mostly Badger, some Paasche and Iwata. Discount sale prices available at businesses like Chicago Airbrush, TCP Global, Coast Airbrush and Webair.
Patrick